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Miscellaneous-Answers to Correspondents.

potash or soda, adding a solution of lead oxide in the
alkali and then boiling. After some minutes the sulphide
of lead separates, and then the excess of lead is removed by
sulphuric acid, and the sulphate removed by filtration.
The filtrate is now evaporated to dryness, the residue
boiled in alcohol and filtered hot. On cooling, the leucine
deposits in pearly crystals. Cystine may be desulphurated
in the same way.
Transformation of Benzoic Anhydride by
Hydrochloric and Hydrosulphuric Acid Gases.
- By passing hydrochloric acid gas over anhydrous
benzoic acid gently warmed, Mosling (Ann. der Chem. und
Pharm., Bd. cxviii. s. 303) procured chloride of benzoyle
and benzoic acid. By means of hydrosulphuric acid he
obtained crystals of what appears to be bisulphide of
benzoyle.

II. ANALYTICAL CHEMISTRY.

Separation of Tartaric and Citric Acids.We find the following method in the Archiv. der Pharm.,

Bd. clviii. s 206. Add to the solution to be tested an

III. TECHNICAL CHEMISTRY.

{CHEMICAL NEWS,

April 1862.

he soaked in ammonia, and hung on a line where the vapour came in contact with it. When the excess of ammonia was dissipated, he took the paper down, wrapped it up carefully, tested it with nitrate of silver, and produced chloride of silver, which showed that he had caught hydrochloric acid gas in the paper. Cross-examined.—Was sure that nothing but hydrochloric acid gas would have produced the same result as he found on his filter-paper. If cyanogen had been on the paper, the appearance and the result would not have been the same; it would throw down a white precipitate; but he could not mistake cyanide of silver for chloride of silver. He could not just then refresh his memory as to which two gases cyanogen was composed of at the moment; some of the compounds of hydrogen were so difficult, that he did not care to speak of them at a moment's notice. Had he met with chlorine on his test-paper, the same precipitate would be deposited, for in the water the chlorine would be formed into hydrochloric acid; but witness was sure the vapour was not chlorine, but hydrochloric acid.

Mr. W. M. WILLIAMS said he was a chemist at Birmingexcess of hydrated oxide of iron, and heat almost to boiling. ham, a Fellow of the Chemical Society, and Lecturer on Allow the excess of iron to deposit, decant the reddish-Theoretical and Practical Chemistry at the Birmingham yellow clear liquid, and evaporate to a syrupy consistence. and Midland Institute. On the 27th of February he was If the citric acid be pure, the residue remains red and clear, but the presence of a very minute quantity of tarnear the defendants' works to discover if there was any taric acid (one centigramme) gives it a cloudiness, and of some 200 yards from the works, and saw distinctly a escape of hydrochloric gas allowed. He was at a distance tartrate of iron is deposited. vapour that came in a direct line from both of the chimneys of the works. He discovered the presence of hydrochloric acid gas by placing on two hillocks pieces of paper, on which he poured liquor ammonia. When the vapour touched the pieces of paper, dense fumes were formed of a peculiar bluish colour, which clearly showed the presence of hydrochloric acid gas. Witness also repeated the test used by Mr. Bird, of catching the vapour in filter-paper which had been soaked in ammonia, and then testing it with nitrate of silver, by which he obtained the characteristic white precipitate nitrate of silver. He further tested the solution with chloride of barium, and that gave no precipitate, which indicated the absence of phosphoric acid, of sulphites or sulphates, and the absence also of arsenic. [The cross-examination of this witness is, unfortunately, not reported, and we can, therefore, take no notice of it.]

Dyeing with Gold. The present is a luxurious age, but we doubt if the following process will come into extensive use. Immerse the silk stuff in a bath of chloride of gold (strength not given) for ten minutes, then wring and dry. At first the silk has a clear straw-coloured shade. When exposed to direct sunlight the colour changes; but the change disappears in the shade. If the free acid is removed from the silk by rinsing in pure water, and the tissue is then spread out in the sun, it soon changes to a beautiful lilac. In summer an hour's exposure suffices, but in winter it often requires some weeks to effect the change. The colour, it is said, has a reddish nuance in direct sunlight and artificial light, but in the shade it looks blue.-Chem. Centralblatt, 1862, s. 32.

MISCELLANEOUS.

CURIOSITIES IN CHEMICAL EVIDENCE.

STAFFORD ASSIZES.-DOWNING V. CHANCE.

THIS was an action brought by a farmer to recover damages for injury done to his crops by the escape of hydrochloric acid from the alkali works of the defendants. The following chemical evidence was given for the plaintiff :

The defence was, that no hydrochloric acid had been allowed to escape the defendants' works since April, 1861, and that the works were surrounded with brick, iron, and phosphate works, from all of which noxious vapours-chlorine, sulphurous, hydrochloric, and arsenious acids3-were evolved. Drs. Wrightson, Hill, and Voelcker, were called on the defendants' side, but we need not quote their evidence. The verdict was entered for the plaintiff, with leave to the defendants to move that the verdict be entered for them.

ANSWERS TO

CORRESPONDENTS.

Mr. ALFRED BIRD said he was a practical chemist, living at Birmingham. He had examined, on September 6, some wheat which had been pointed out to him; the ears appeared to have suffered an unusual injury, the grains were not properly formed, and the whole of the crop appeared and Advertisements and Business Communications to the PUBLISHER at

more or less out of health. This he believed to have been caused by some burning or corrosive agent, and muriatic acid gas would have the effect. In the manufacture of soda from salt, the chlorine was liberated by the addition of sulphuric acid, and the chlorine, mixed with the hydrogen of the water, took the form of muriatic acid gas-a gas most poisonous to vegetation. There was no affinity between the smell of muriatic acid gas and the smell from iron or brick works. On September 6 the wind was from the direction of defendants' works, and the smell of muriatic acid gas was unmistakable. When this gas came in contact with ammonia, it formed sal-ammoniac, and when it approached ammonia the vapour assumed a denser and bluish appearance, consequent on the formation of chloride of ammonia. Witness took a sheet of filter-paper, which

All Editorial Communications are to be addressed to the EDITOR; the Office, 1, Wine Office Court, Fleet Street, London, E.C.

In publishing letters from our Correspondents we do not thereby adopt the views of the writers. Our intention to give both sides of a question will frequently oblige us to publish opinions with which we do not agree.

Carbolic Acid.-We are informed that this valuable disinfectant may be obtained at the Tower Chemical Company's Works, Droylsden, near Manchester. J. G. Tutters-1. We do not know the details of the process. letter addressed to Mr. Brady, M.P., House of Commons, will find 3. The date of any patent can be obtained at the Patent Office, Southampton Buildings.

him.

2. A

F. C. In testing solutions containing magnesia, you must have chloride of ammonium present, or the magnesia will pe partially precipitated by several reagents in the wrong place, and may be P. S. M.-Apply to Professor Redwood, 17, Bloomsbury Square.

mistaken for other earths.

THE CHEMICAL NEWS.

VOL. V. No. 123.-April 12, 1862.

SCIENTIFIC AND ANALYTICAL CHEMISTRY.

On Soil-Analysis, by Professor S. W. JOHNSON,
of Yale College.
(Continued from page 170.)

HAVING shown how small an error in sampling may affect the chemist's estimate of a soil, it is not out of place to insist for a moment that a similar error in the analysis itself must have the same result. In running over 200 pages of Dr. Peter's Fourth Kentucky Report, we find five analyses of soil in which there is a gain of from five to eight-tenths per cent.; we find twenty-three in which there is a loss exceeding five-tenths per cent. In thirteen of the latter the loss is eight or more tenths, in eight instances the loss is one per cent. or more, and in one case is one and eight-tenths per cent. We should scorn to notice little matters like these, errors which are inseparable from the best manipulation and the best processes, were it not that in soil analysis it is precisely the small quantities which alone have any importance.

We find in Dr. Peter's work, as in the work of all who have preceded him in the analysis of soils, from Davy and Sprengel downwards, evidence that the best endeavours in this line of research are entirely in commensurate with the desired results.

It may be objected to this criticism of the analyses, that the loss or gain must be distributed among the twelve ingredients determined. It is true that there is a probability that such distribution would be just; but this is by no means certain, and it is equally true that, this being done, there is still force in the criticism, for the four-tenths per cent. of the soil which a century of wheat crops would remove likewise consists of twelve ingredients.

The second result of these analyses, according to Drs. Owen and Peter, is what the former (Fourth Kentucky Report, p. 33) declares to be "a general law""now established," viz. "that soil analysis is capable of showing the exhaustion in land of the mineral food of plants by continual cropping."

To show the removal of soil ingredients by cropping, the plan was followed of collecting soils from contiguous fields, one of which had been "cultivated," while the other was in its virgin state. On comparing the analyses it was found that in seventy-one cases out of seventynine a loss had occurred in the soil which had been in use without manure from ten to fifty years. In eight instances, however, the analysis failed to show such a result, owing to local causes, the soil of the old field being based on a sub-soil richer than was the virgin field, or the old field having received washings of more elevated lands, &c.

The admitted richness of the old over the new soil in

* Misprinted twenty-one, on p 31, Fourth Kentucky Report.

these eight exceptional cases is expressed by hundredths of per cent., e.g., soil Nos. 982, virgin, and 983, cultivated, differ by o066 per cent. of potash. Soils 1144 and 1146 by 0032 per cent. of phosphoric acid. Soils 1204 and 1205 by o'092 per cent. phosphoric acid. Soils 1207 and 1208 by 0.033 per cent. potash. Similar fractions likewise show the amount of deterioration in the other seventy-one cases. We adduce two instances pointed out by Dr. Peter in the Third Kentucky Report, P. 207, and one given on p. 176 of the Second Arkansas Report Carb, of lime. Magnesia. 0'335

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Virgin soil, No. 557. 0345 Old soil, No. 558.

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Phos. acid. Potash.

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Virgin soil, No. 288. 0 121 Old field, No. 289 . 0.021 Difference

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We were prepared to find these differences much larger. It is seen at a glance that they fall within the errors of Dr. Peter's own manipulation, and when we assert, that of ten analyses of the most homogeneous material made by the same analyst under the most favourable circumstances, five would differ among each other by an amount equal to the quantities upon which this "natural law" is supported, we a scrt what every competent analyst knows to be true, and what moreover pronounces most emphatically upon the value of such investigations.

It is therefore our conclusion, that while, as has long been known, the soil loses in mineral matter what the crop gains, it is doubtful if in any given case chemical analysis can indicate this difference with certainty, for the reasons that the accidents which affect analysis make the limits of inaccuracy to cover more than the loss by years of cropping. When we take into account the changes that are constantly progressing in the soil when under cultivation-changes by which the disintegration is hastened, changes by which it is made, in many instances, more retentive of soluble matters-when we

remember that most cultivated crops, although they carry off in seed, stem, and foliage, a quantity of mineral matters, yet derive these in part from a depth below the range of analysis, and in their roots or stubble leave upon the surface salts brought up from a considerable depth-we perceive that the problem is so complicated with compensations and variable quantities as to put it beyond the reach of quantitative chemical analysis.

If, in any case, soil analysis does show, or appear to show, the exhaustion of the soil, it is, however, the appeal to experience which proves it; and as this is the first, most obvious, and an entirely sufficient proof, we

+ Misprinted on p. 207, Third Kentucky Report, where the difference is inade o'045 instead of 0-078, as given above from the tabulat.d analyses.

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do not see the value of the "law" that has 10 per cent. (eight-seventy-ninths) of exceptions, the existence of which, like that of the rule itself, is only to be established by comparison with the plain agricultural fact.

In short, if we admit the result as Drs. Owen and Peter would have it, of what use or interest is it?

CHEMICAL NEWS,
April 12, 1862.

A careful examination of the analyses recorded in the Arkansas survey shows that the average composition of the eight soils analysed from the lower silurian and of the fourteen from the millstone grit compare as follows, in regard to the more important ingredients :Carb. Mag- Phos, Sulph. lime nesia. acid. acid. Potash. 0355

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Millstone grit,
0215 0531 0'180 0'057 0148
Here we see that the soils of the poorest formation
are inferior to those of the richest only in carbonate of
lime and potash. Of the soils of the millstone grit, nine
are richer in carbonate of lime than the poorest of the
silurian, and five of the former contain more potash
than the poorest of the latter. On the other hand,
but two of the silurian soils have higher per-centages
of either carbonate of lime or potash than the richest
soil of the millstone grit. If these figures demonstrate
anything, it is the fact that no geological formation has
the absolute monopoly of either barren or fertile soils.
If the analyses of Dr. Peter show the "peculiarities
of the soils of any geological age, then certainly these
peculiarities are not remarkably peculiar !"

On page 50 of the Second Arkansas Report, Dr. Owen remarks as follows:

The third point is, that analysis shows "the peculiari-Lower silurian, average of 8 soils ties of the soils derived from different geological formations." Says Dr. Owen," These analyses most distinctly show that certain geological formations impart to the soil more of the important mineral fertilisers than others." The reader will be able to see that it is those formations which are composed of easily disintegrating materials which, all other things being equal, yield the soils richest in phosphoric acid, lime, and potash, and at the same time contain the quantity of alumina and oxide of iron necessary to render them sufficiently retentive and attractive of atmospheric water and ammonia; therefore these soils are the best adapted for those grains and crops which require the largest proportion of these ingredients." "He will, moreover, be able to trace the gradual diminution in the proportion of the more important mineral ingredients, down from these extraordinarily fertile soils derived from the highly fossiliferous, argillo-calcareous beds of the lower silurian, the "With the table of the composition of the ashes of cretaceous, and the tertiary systems of the West; plants to refer to, appended to this report, and after through the silico-calcareous soils of the upper silurian, becoming acquainted with the usual proportions of devonian, and sub-carboniferous limestone strata, in mineral constituents in an average soil,-information which fossils are either more sparingly distributed, or which is easily acquired by looking over the table of in some cases almost wanting, and which are far less soil analyses in this report,-it is easy for any indieasy of decomposition; thence through the argillo-sili-vidual to see, when he is provided with a reliable analysis cious soils of the coal measures with only locally organic of his soil, not only to what crop it is best adapted, but remains, and these chiefly of plants, down to the more what kind of mineral fertilisers, if any, it requires as a purely silicious soils prevalent where the non-fossili- manure, and how it compares in fertility to the various ferous sandstones of the coal measures and of the mill-grades of soils from other farms and other States. Is stone grit, prevail to the exclusion of either shales or not this knowledge of some value to the farmer? " limestones, and which afford the most unproductive soils as yet analysed." While it is to be expected that rocks of complex origin rich in organic remains-which are evidences that the rocks themselves originally resulted from the deposition of the washings of fertile lands-should yield richer soils than sandstones or limestones, we do not see that analysis of the soil makes the fact more evident. Knowledge of the composition of a rock enables us to judge in a general way of the value of the soil, so far as this depends upon chemical characters. We do not see what is gained by further analyses of the soil. It would appear that the cheap mental processes of deduction or inference may accomplish here in a moment all that an expensive analysis Pan show.

We fail, moreover, to perceive that analysis shows "the peculiarities of the so ls derived from the different geological formations." In a cretaceous or limestone soil we of course expect to find much carbonate of lime, and in a sandstone or millstone grit soil much insoluble silica or silicates, but the quantities of phosphoric acid, potash, and sulphuric acid do not appear to bear any definite relation to their geological origin. It is impossible to represent the composition of the soil of any geological formation by a typical statement of percentages, or to point out its peculiarities further than by an undefinable more or less. Although Kentucky and Arkansas lie mostly or altogether beyond the influence of drift, yet the action of running water in its Constant passage from hill-top to valley has to a great degree obliterated from the soils those peculiar differences to be found among the rocks from which they have been derived.

The above, we are of opinion, proceeded rather from the generous heart than from the critical brain of its lamented author. Had he attempted to do the things which he believed to be so easy, we are sure his statements would have lost somewhat of their directness, and would have appeared in a form highly modified from the above. "The usual proportion of ingredients in an average soil." What is an average soil? Our only way of deciding what is such a soil consists in noting the average yield of soils. But the yield depends not alone on the soil, but upon climate, weather, tillage, and various incidents and accidents. It depends not on the composition of the soil, not on the "proportion of ingredients" alone, but likewise on the condition of those ingredients, their state of combination, their solubility. It depends also on the physical characters of the soil, which determine the relations of the crop to the essential conditions of regulated heat and moisture. The soil is not less important to the plant in its function of home than in its function of food, the lodgings are of equal influence with the board. It is a nice work to balance these varying circumstances, many of which have as yet in our science no shadow of a numerical expression, and then to say how many thousandths of a per cent. of potash, lime, phosphoric acid, &c., belong to the " average soil."

Dr. Peter has, indeed, attempted to show the degree of availability of the elements of the soil by the following process:-"A quantity, generally thirty grammes, of the air-dried soil is placed in an eight-ounce strong vial, with a close fitting stopper, and the bottle is filled up with distilled water which has been charged with pure carbonic acid gas, under a pressure of about two

atmospheres. The bottle is allowed to remain for about a month at a temperature about that of summer heat." The matters thus dissolved were then analysed as usual. These results have this value, they show that the water of the soil is capable of dissolving all the elements of the food of plants. They furnish, moreover, a rough comparative view of the available matters in different soils. Beyond this we cannot attach any value to them. (To be continued.)

On the Commercial Analysis of Chrome Ores, by CHARLES O'NEILL, F.CS., Author of Chemistry of Calico Printing and Dyeing."

DURING the last two years, I have analysed nearly 200 samples of chrome ore, principally from America, and chiefly in the interest of consumers here. I have been frequently brought into conflict, in an indirect manner, with foreign analysts, on account of the discrepancy between my results and theirs. These differences have ranged from 5 to 25 per cent. of green oxide of chromium, my determinations being invariably less than those returned by the American chemists. Chrome ore is sold by its per-centage of chromic acid, calculated from the green oxide obtained, and very much dissatisfaction has, of course, arisen from the importers having to pay for a considerably higher per-centage than actually existed. The large consumers of chrome ores generally accept bills for the cargoes long before they arrive, and, as there appears to be no legal remedy for them when they discover the inferior quality of their ore, the complaints and correspon dence have been numerous and unpleasant. There is nothing really new in the system of analysis which I follow, excepting the combination of treatments which the ore receives; it has the merit of being expeditious, and is sufficiently exact for all commercial requirements. I shall give it in detail, and if it has any defects I have no doubt they will be soon pointed out.

1. Grinding of the Ore. The ore is sent for analysis in three states: either, first, massive, in lumps of two or three ounces each, called rock ore; secondly, in a granular state, called sand ore; or, thirdly, rather finely-ground, as it is used in the bichrome manufacture. A fair sample is taken, and reduced to a tolerably fine powder in an iron mortar. I weigh 6 grains of this upon a common balance, and grind in an agate mortar, taking 2 grains only at once; the grinding requires twenty minutes. I consider it sufficiently ground when all gritting-sound or feeling has disappeared, and the ore forms flat cakes rising under the pestle. The success of the analysis depends altogether upon the grinding, which must be scrupulously attended to; the caking mass of ore must be several times swept together with a trimmed quill or a stiff hair pencil, and spread out again with the pestle, so as to thoroughly crush every particle. The ground ore is then placed in a balanced watch glass, and 51 grains of it taken. The usual qualities of ore are very little hygrometric, and present no difficulties in weighing.

2. Fusion with Bisulphate of Potash.-I prepare bisulphate of potash by acting upon pure nitrate of potash with sulphuric acid, fusing the whole at a red heat in a platinum capsule, and pouring to cool on a stone slab. Sixty grains of this are coarsely pulverised and placed in a platinum crucible, so large that the bisulphate when fused only rises one-fourth its height. The ore is then swept on the bisulphate, lightly mixed with it by means of a wire, and the whole exposed to heat for

twenty minutes. The mass must be maintained in perfect and quiet fusion for ten minutes; for the first few minutes care must be taken that the fused mass does not rise over the edge of the crucible. When cooled, the mass must be detached from the crucible, by gently pressing the sides of the crucible, and received into a porcelain dish, where it is treated with water until entirely dissolved or disintegrated. If the mass comes out of the crucible in a solid lump, this dissolution will take a considerable time. I avoid this inconvenience by taking the red-hot crucible with a forceps, and cause in a thin crust, easily detached from the crucible, and the molten mass to flow round the sides, where it cools readily acted upon by water.

3. Precipitation of the Mixed Oxides.—Car. bonate of soda is added to the acid mixture until it is strongly alkaline; the precipitate thrown upon a filter and slightly washed; then drained and dried as quickly as possible. Up to this treatment, the process is exactly that given by Hunt, fifteen years ago. If there be any ore unacted upon, it is visible here as a heavy, black, crystalline, or granular powder, easily discernible in the white dish. I never have a trace of this black powder visible; but young pupils, making an analysis, never fail to see it, either because they have not had patience in grinding or they have not had sufficient strength of wrist and thumb to effectually crush the ore.

4. Fusion with Carbonate of Soda and Chlorate

of Potash.-A mixture is made of two parts by weight of powdered chlorate of potash and three parts of pure dry carbonate of soda; seventy grains of such a mixture is taken, and the greater portion thrown into a small glass mortar. The dried precipitate is detached as much as possible from the filter, allowing it to fall on the mixed carbonate and chlorate. The filter is then carefully burned, and the ashes added to the contents of the mortar; the precipitate is carefully mixed up with the alkaline and oxidising mixture, by means of a glass pestle, and the whole transferred to a platinum crucible; the remaining chlorate and carbonate serve to rinse out the mortar. The whole is mixed up with a wire, and exposed to a gradually-increasing heat until in perfect fusion, and kept so for ten minutes; the whole time of heating is from twenty to thirty minutes. Some ores, which contain a good deal of magnesia and silica, are difficult to fuse, and require the heat of a muffle, but for ordinary ones a Bunsen's burner suffices very well, and twenty minutes is long enough for the fusion. The fused mass is cooled, dissolved in hot water, and filtered from the oxide of iron, &c., the filter being well washed. Any undecomposed ore remaining will be found on the filter, and may be rendered visible by boiling its contents with hydrochloric acid. The substitution of chlorate of potash for nitrate was rendered necessary by the subsequent method of determining the chromic acid in solution. With nitrate of potash there is nearly always production of alkaline nitrite, or some other compound of the lower oxides of nitrogen, which causes the evolution of nitric oxide upon addition of acid, and the consequent partial or total reduction of the chromic acid. Chlorate of potash is easily and wholly decomposed by heat. I have never found any chlorate or perchlorate left after an ordinary fusion.

5. Estimation of the Chromic Acid.-I use a volumetrical method, depending upon the capability of sulphurous acid to deoxidise chromic acid the ordinary temperature in presence of fres prepare a strong solution of bise passing sulphurous acid

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200

Preparation of Pure Nitrate of Silver.

tion, and then make it alkaline with caustic soda, so as to have a neutral sulphite, which is less readily oxidised by keeping than the bisulphite. I use a dilute solution made from this concentrated sulphite, of such a strength that one grain of pure bichromate of potash requires about, and not less than, 200 grains measure of the sulphite to deoxidise it. The value of the sulphite must be determined for every operation, since it is continually absorbing oxygen. This is done twice by weighing out three grains and four grains of pure bichromate, dissolving each of them in ten ounces of water and acidulating freely with sulphuric acid, then adding the sulphite from the burette, with continual stirring, until the chromic acid is destroyed. The stopping-point may be ascertained by the colour when one is accustomed to the reaction, but even an experienced eye will often be glad of additional evidence. A mixture of iodide of potassium and boiled starch, slightly acidulated, forms a delicate test; it has usually a faint colour, which is even preferable to a colourless mixture. An exceedingly small quantity of chromic acid developes the blue colour in spots of this mixture, and a very slight excess of sulphite makes it colourless. One division of the sulphite test-liquor, or 005 grains of bichromate of potash in twelve ounces of water, easily and quickly influences the test mixture, The chromate from the chrome ore is tested in the same manner, and the quantity of oxide of chromium or chromic acid calculated from the equivalents of bichromate of potash. The tenth of a grain more than five taken is to allow for all losses, and the results are multiplied by twenty for the per-centage. 151 of bichromate of potash is reckoned equivalent to 80 of green oxide of chromium, and 104 of chromic acid. A determination can be made by this process in three or four hours, and a double determination in a little longer time. I usually make two analyses, and reject them if they present a difference of more than two per cent. of oxide of chromium; usually the results are within one per cent.

CHEMICAL NEWS,
April 12, 1862.

I find that the bulk of American chrome ore contains from thirty to thirty-five per cent of oxide of chromium. The richest ore I ever examined was massive rock ore, which contained fifty-eight per cent. of sesquioxide of chromium. I have examined specimens of titaniferous iron sand, sold to manufacturers and applied by them as chrome ore, which contained less than one per cent. of oxide of chromium. Other samples of ore contained three to seven per cent., but thirty per cent. is a good average. It is in the argillaceous chrome ores that the greatest difference of results have been obtained by myself and the American analysts. One sample, sold as an ore of thirty-four per cent., only yielded to me nine per cent. This error was admitted and explained by saying that the method of analysis was found not applicable to ores containing much clay. I believe if the Transatlantic analysts were to analyse their precipitates of the sesquioxide of chromium, they would find them to contain magnesia, silica, and sometimes alumina. I consider their determinations can only be correct in ores free from silica, magnesia, and alumina, and these are very rare.

92, Grosvenor-street, Manchester.

TECHNICAL CHEMISTRY.

On the Construction of Basins and Reservoirs Unattackable by most Acid or Alkaline Liquids, by M. H. KALISCH.

UNLESS by making use of wrought or cast iron (which have the inconvenience of being easily attacked by all acid liquids), it has been found very difficult to construct reservoirs capable of resisting the action of boiling solutions of caustic alkalies.

Most of the materials or luting proposed for this purpose are either much too easily acted on, or are too expensive for application on a certain scale.

The author proposes to line the sides of such stone reservoirs with plates or slabs of heavy spar (native sulphate of baryta), and to cement all the joints with a luting prepared in the following manner :

baryta.

Reservoirs constructed in this way ought to resist not only the corrosive action of boiling caustic alkalies, but most organic or inorganic salts,-for instance, sulphates, chlorides and nitrates of zinc, iron, copper, soluble glass, cream of tartar, &c., and boiling hydrochloric, phosphoric, boracic, oxalic, tartaric, and citric acids, and slightly diluted cold sulphuric acid. — Repertoire de Chimie, iii. 474.

I have been favoured with an outline of the method of analysis followed by one of the American chemists whose results differ from mine. The ore is ground, half a Digest one part of india-rubber, in small pieces, with gramme being taken, fused with bisulphate for a much two parts of freshly rectified spirit of turpentine until longer time than I think necessary, and then, without the mixture becomes perfectly homogeneous, then incorremoving the fused mass, the necessary quantity of car-porate with it four parts of powdered sulphate of bonate of soda and nitrate of potash added, and the whole fused again; the resulting mass digested a long time with water and filtered; the filtrate mixed with carbonate of ammonia, and kept in a warm place for some hours, to precipitate alumina; the liquor again filtered, acidulated, and the chromic acid reduced by sulphurous acid; excess of ammonia added to precipitate the oxide of chromium, which is collected upon a filter and weighed in the usual manner. I think this process may be called a bad modification of Hunt's. There would be a saving of time and trouble if the alkaline and oxidising mixture could be added to the bisulphate as directed; but from two or three attempts I made, I found it impracticable without having platinum crucibles of an excessive size, or else previously heating the bisulphate so intensely as to expel entirely the extra atom of sulphuric acid. The fluid containing the chromic acid will contain likewise alumina, silica, magnesia usually, and titanic acid sometimes. The carbonate of ammonia may remove the alumina, but it will not remove the silica and magnesia. These, I believe, will be precipitated, wholly or in part, with the oxide of chromium, whence, I presume, the discrepancies complained of.

Preparation of Pure Nitrate of Silver, by M. LIENAU. ATTACK cuprous silver containing copper by nitric acid; to the solution, sufficiently concentrated, add chlorine water, freshly prepared, which precipitates the silver only. Then wash the precipitate in chlorine water, which prevents the chloride of silver from decomposing under the influence of light, and renders it more speedily soluble in ammonia; when well washed, dissolve it in the liquid, and plunge into the solution a well cleaned copper-wire. As the copper dissolves, the silver is precipitated, and is deposited as a brown powder; the operation is at an end when the wire preserves its brightness after being washed in water.

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