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THE CHEMICAL NEWS.

VOL. V. No. 131.-June 7, 1862.

THE PATENT LAWS.

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ON last Tuesday week, Sir Hugh Cairns brought forward in the House of Commons his long-threatened motion for a Royal Commission to inquire into the operation of the Patent Laws. It is needless to say the motion was carried without a division. The whole policy of the Patent Law will now be brought under consideration, and the opponents and supporters of grants of monopoly will have a fair opportunity of urging their various opinions. Our own views on the subject may be stated in a very few words. We believe it is only right that an original inventor should be secured, as far as possible, some reward for his ingenuity; and this perhaps is best accomplished by giving him for a time a monopoly in his invention. But we have no doubt that we shall fairly state the opinion of all disinterested readers when we say that but one claim for a monopoly should be allowed, and that is, the novelty or the originality of the invention. This satisfactorily established, the right to protection, we think, is indubitable. But it is clear that, proceeding on this idea, an entirely different method of granting patents must be adopted. At present, as Sir Hugh Cairns stated, the only investigation which alleged inventors undergo before patents are granted is conducted by the law officers of the Crown, and is confined to the descriptions in the specifications. Of the novelty or usefulness of an invention they, of course, can be no judges. As regards the usefulness, about which so much parade is made in a patent, we believe that that may be left entirely out of the question. If an invention is not useful, there will be small advantage in obtaining a patent for it. The novelty, however, is a matter deserving some investigation, and this could only be conducted by persons well acquainted with the subjects concerned. Speaking as a lawyer, Sir Hugh is of course opposed to any preliminary scientific investigation. This, to a legal mind, we have no doubt, would appear the height of absurdity. It is so much more simple and reasonable for any one to get a patent revoked by applying for a rule to show cause, or something of that sort, by which a person might be called on to justify his patent, and thus the air might be cleared, and the manufacturing public would be, at a small expense, disembarrassed of worthless and trivial patents." No doubt of it, if any one would take the trouble; but unfortunately such a "short and simple mode" might have another effect different to that contemplated. Probably if Sir Hugh had set his wits to work to see in what way a grasping and litigious capitalist might most easily rob an inventor of the fruits of his ingenuity and industry, he could not have proposed a better scheme than the one suggested above. Most likely in the end it would be found quite as expensive to justify a patent as to prosecute for infringements; and another legal reformer coming a few years after Sir Hugh, would have equally gross instances of expensive litigation to quote, and, we believe, with greater wrong done.

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"The vice of

The whole reasoning of Sir Hugh on this part of the subject is so well answered in the Times that we shall make no excuse for quoting the passage. too many inventions now patented," says the Times, "is not their want of utility, but their want of novelty, or rather their suspicious resemblance to some other contrivance already in use; and that is a point quite capable of being sifted. Nothing can be more impolitic than to grant a lucrative and exceptional right as a matter of form, on the chance that, if it should have been granted in error, some one will move for its revocation, though not, perhaps, till after it has been transferred by assignments and deeds of licence to a dozen different persons." And so, we may add, been proved to be of sufficient value to make it worth disputing. Nobody would think of going to law about a "worthless or a trivial patent;" but there are people who would move all the Courts at And then, argues Westminster to upset a valuable onc. Sir Hugh, scientific men are so sceptical and prejudiced, that they cannot be trusted to give an opinion as to the novelty or usefulness of an invention. Sir Humphry Davy, he says, did not believe in the possibility of lighting houses with gas, and had he been acting as a judge, he would have condemned that invention as useless. We do not believe that Sir Humphry would have done anything so absurd. If an inventor had come forward professing to accomplish what had before been deemed impossible, Sir Humphry Davy, like a sensible man, would have considered it the strongest ground for granting him a patent, and would have left him to demonstrate the practicability of his scheme when he had been fairly protected. Sir Humphry might have objected, he did so, in fact,-to the lighting of a house with gas as dangerous, but he would never have con

demned the invention as useless.

Taking chemical patents as illustrations, and not being lawyers, we believe that the manufacturing public would be most easily disembarrassed of worthless and trivial patents if the specifications of the alleged inventors were submitted to a competent chemical authority before the patent was granted. It would be invidious now to mention special instances; but any reader of the CHEMICAL NEWS, or any person having much acquaintance with chemical patents, will remember numerous cases in which they ought never to have been granted. The ideas in these patents have not the least show of novelty, they may even be found in a familiar manual; but an insidious wording of the specification and the claim opens the matter for litigation if it should ever turn out worth disputing, and most manufacturers, unless very wealthy, would rather pay for a licence than defend an action for infringement.

With all that fell from Sir Hugh Cairns respecting the tribunals for the trial of patent cases, we fully agree. He seems inclined to accede to the proposal for scientific assessors, which we advocated some weeks ago, but expressed no decided opinion on that point. It is hard to

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On the Presence of Rubidium in Certain Vegetable Substances. {CHEMICAL NEWS,

see why, if scientific assessors may advise a judge in the trial of patent disputes, scientific commissioners may not advise the Attorney-General in granting patent rights, except, by the way, that the latter proceeding might perhaps render much of the former impossible.

SCIENTIFIC AND ANALYTICAL CHEMISTRY.

On the Presence of Rubidium in Certain Vegetable Substances (Beet-root, Tobacco, Tea, Coffee, Grapes), by M. L. GRANDEAU.

ON the 24th of February last, I had the honour to communicate to the Academy the results of my researches on the presence of rubidium in the salts from beet-root, and in the mother-liquors obtained from treating them for the extraction of chloride of potassium. Since then I have actively pursued this research, both in the laboratory of the upper Ecole Normale and also in the important factory of M. Lefebvre, distiller at Corbehem, who has kindly placed at my disposal the substances necessary for extracting chloride of rubidium on a larger

scale.

Thanks to this assistance, I now possess 400 grammes of pure chloride of rubidium, about half of which has been prepared at the factory at Corbehem, according to my instructions, by the assistance of M. Martel, a skilful young chemist attached to M. Lefebvre's establishment. When presenting to the Academy, at a subsequent sitting, the new salts of rubidium which I had been able to prepare from the pure chloride at my disposal, I will describe the processes which I have employed for the extraction of the chloride, and will show by the aid of a few figures that the quantity of rubidium annually removed from one hectare of land by beet-root is an amount not to be neglected from an agricultural point of view.

I now propose to submit to the Academy some new results, proving the great dissemination of rubidium in nature. Having found the new metal in the salts from beet-root, which it is known are very rich in potash, it seemed of interest to seek for it in other vegetable substances, which, by the readiness with which they remove potash salts from the soil, more or less approach beetroot in this respect. I will confine myself in this extract to point out the analytical results which I have obtained, omitting the methods of separation and analyses given in my memoir.

1. Tobacco. I have at present only examined the ieaves from Kentucky and Havannah. M. Schlesing, Directeur de l'Ecole d'Application des Tabacs, has been good enough to evaporate to dryness in his laboratory a certain quantity of water which had been used for the prolonged washing of Kentucky leaves. The ignited residue was tolerably white, spongy, and very rich in potash. On spectral analysis this residue gave the characteristic lines of lime, lithium, potassium, and rubidium. The quantity of lithia was very slight. There was, on the other hand, a notable quantity of

rubidiurn.

Leaves from Havannah, best quality, were carefully burnt; their ashes gave me on analysis results identical with those obtained from the Kentucky leaves.

June 7, 1862.

of rubidium, but not a trace of lithium. Coffee is much richer in rubidium than tobacco.

3. Grapes (crude tartar).—M. Kestner, of Thaun, has kindly sent me, at my request, some mother-liquors obtained in the treatment of crude tartars. These liquids were freed from organic matters and foreign substances which they contained, and the residues then submitted to spectral analysis. I am able to state definitely that they contain rubidium, but in very small quantity.

It appears certain from these facts that rubidium is one of the most widely distributed simple bodies in nature. The most different vegetable bodies from the most distant localities remove it from the soil. Moreover, it is evident from my researches that the presence of rubidium is not necessarily allied with that of lithium, as might have been imagined from the analyses of minerals and waters in which M. Bunsen has discovered this metal. I ought to add that several vegetable bodies of which I examined the ashes appeared to contain no rubidium, although many of them were rich in potash. I may especially mention as instances the colza, the cacao, the sugar-cane, and some species of fucus.

The dissemination of the new alkaline metal being placed beyond doubt by the researches of which this is a résumé, it is of great interest to examine with this particular object the soils in which the above-mentioned vegetables grow. With this view I have undertaken experiments and analyses, which I am pursuing as rapidly as the long and delicate character of these investigations will allow.-Comptes-Rendus.

On the Production of Nitrate of Methyl,

by M. CAREY LEA, of Philadelphia. FOR the production of nitrate of methyl but one process appears to have been proposed, and that is to be found in all our text-books, English, German, and French. Two parts of powdered nitre are to be distilled in a capacious flask with a recently prepared mixture of 5 parts wood spirit and ro oil of vitriol. Judging from the reactions of ethylic alcohol, it did not appear to me probable that such a proceeding could succeed. It was tried, however, and with the following results.

The substances were placed in a flask capable of containing twenty times their united volume, which was connected with a Liebig's condenser by a wide delivery tube. For a few minutes no action was perceptible, but it soon set in, with rapidly increasing violence. Torrents of gaseous products with deep red fumes of oxides of nitrogen were evolved, and presently the apparatus blew up with a loud explosion, and had not due precaution been taken with a view to a possible unpleasant conclusion, personal inconvenience might have resulted, for the 3-litre flask was shattered into very small pieces, which were thrown to a considerable distance. quantities operated upon were small; 50 grammes of methylic alcohol and proportionate quantities of the other substances. No heat was applied.

The

It is scarcely probable that the gases were evolved in such quantities as to have caused the explosion. It seems more likely that the heat generated by the reaction was sufficient to raise the temperature of the interior of the flask to 150° C., at or below which point, according to Dumas, the vapour of methylic nitrate explodes.

2. Coffee and Tea.-Coffee and tea completely and carefully incinerated left ashes rich in potash. An I have had no difficulty, however, in preparing this examination of these ashes, after appropriate treatment, ether by a different process. By dissolving a considershowed in each of these products considerable quantities | able quantity of urea or nitrate of urea in methylic

alcohol, it supports the action of nitric acid with the utmost facility. The following are the proportions which I have employed.

Into a retort of the capacity of a litre, 200 c.c. of purified wood spirit are placed, and about 40 grammes of nitrate of urea are added and heat applied. When solution has nearly taken place, 150 c.c. of nitric acid, free from the lower oxides of nitrogen, sp. gr. 131, are added, and the mixture is distilled to one-third. 170 c.c. of wood spirit and 130 of nitric acid are then added and distilled to the same point. Finally, 150 c.c. wood spirit and 110 nitric acid, with 10 grammes of nitrate of urea, are added, and distilled to the same point as before. It is useless to carry the distillation further than the point here specified, not that it is accompanied by any inconvenience, but because nitrate of methyl ceases to be evolved. The temperature rises very high at the close of the distillation.

The operation may be carried on rapidly. We are recommended in the text-books to carry off the vapours very carefully in preparing nitrate of methyl, on account of the production of cyanhydric acid as a by-product. In chemical laboratories there is, doubtless, generally rather too little precaution taken than too much against noxious vapours; but in the present case I have carefully examined the distillate, both in the old process, which failed, and in that which I here propose, and I could find no trace of cyanhydric acid either by the iron or the silver tests, or by conversion into sulphocyanide. Both the ether itself and the watery part of the distillate were tested. As, however, it is impossible without special analysis to know what impurities may be present in so variable a substance as commercial wood spirit, it is difficult to foresee what substances may be generated in its decomposition; but I think I am justified in concluding that cyanhydric acid is not generated by the action of nitric acid upon methylic alcohol; at least, not in the presence of urea.

Treated as above described, 420 grammes of wood spirit yielded a distillate, from which by agitation with solution of salt there separated the very large quantity of 300 grammes crude nitrate of methyl. This may be subsequently agitated with a little weak solution of carbonated alkali.

The wood spirit before use should be distilled with one-third of its bulk of very strong (almost saturated) solution of caustic soda, to decompose any acetate of methyl which may be present. This operation must be performed over the water bath.-Amer. Jour. Science and Arts.

tated metallic copper is then separated by filtration and the liquid slowly evaporated. If, during evaporation, the neutral solution of sulphate of cadmium should deposit a small quantity of sesquioxide of iron, which not only constitutes an impurity, but gives the salt a bad appearance, it is necessary to expose the solution to the atmosphere until all the iron which it may contain has been eliminated, which is accomplished when, after a second filtration, the transparency of the solution is no longer disturbed. To obtain finally the sulphate of cadmium in well-formed crystals, it is necessary to acidulate the solution slightly with dilute sulphuric acid. Journ. Md. Col. of Pharm.

New Method of Estimating Alkaline Hydrates and Carbonates, and other Compounds of this Class, by M. PERSOZ.

IN a recent number of the Annales du Conservatoire des Arts et Metiers a new method of estimating nitric acid was described, founded on the following facts:

1. Fluorides, chlorides, bromides, and anhydrous alkaline sulphates are not decomposable by potassic bichromate heated to fusing point, and even to nascent red heat.

2. All nitrates are decomposable under these conditions. Nitric acid is completely expelled in proportion as chromic supplies its place, and an equivalent quantity of chromate is produced.

Now, in applying this method to the estimation of certain commercial salts of soda,-mixed with carbonate, chloride, sulphate, and nitrate,-which are frequently sent to the laboratory of the Chamber of Commerce, which salts sometimes contain as much as 19 per cent. of nitrate, I found that by heating with precaution a mixture of these salts and bichromate, taking care not to raise the temperature sensibly beyond the fusion point of the latter, that the whole of the carbonic acid was expelled without taking the nitric acid with it.

It is evident that we here have the means of determining through successive losses estimated by weighing first the carbonic and then the nitric acid. As the loss of nitric acid in a well conducted operation corresponds exactly with the alkalimetric standard, one more step only is necessary to the formation of a rational method of estimating commercial alkaline carbonates without having to fear, in certain cases, the errors inevitable to the employment of the ordinary methods, and owing to the presence of alkaline sulphides, oxisulphides, lime, sulphites, and hyposulphites, &c.

It is easy to understand, and it has been ascertained A Quick and Easy Method of Preparing Sulphate of by direct experiments, that potassic bichromate either

Cadmium.

oxidises or saturates oxisulphides, sulphides, sulphites, hyposulphites, and lime without causing any disengageTHIS method, adopted by the author, is nothing more ment. A carbonate, on the contrary, decomposed by than the application of the fact observed in 1792 by potassic bichromate occasioned a disengagement of carRichter, that a metal plunged into a saline solution sub-bonic acid exactly proportioned to the amount of the stitutes itself for the metal, which forms the base of the salt employed. A quantity of crystallised sulphate of copper, say 100 grammes, is dissolved in water, and a piece of cadmium, rather more than is necessary to saturate all the sulphuric acid, or in this case more than 44 59 grammes, is plunged into the solution. The whole having been allowed to stand for some time, the precipi

Freedom from the lower oxides is an essential condition of success. That nitric acid is colourless is not in itself a sufficient indication of purity in this respect. An acid which causes the least darkening to a solution of ferrous sulphate is wholly unfit for use in the preparation of either methylic or ethylic nitrate.

base which retained it in combination. A hydrate equally disengaged a quantity of water corresponding to a simple hydrate or to a bihydrate, according to the temperature employed.

It only remained to devise an apparatus so to conduct the experiment that the products of the reaction might be collected. Liebig's apparatus was ready to our hand, and this, slightly modified, was employed to analyse the organic matters. We used then a combustion tube from 50 to 60 centimètres long, very slightly curved in the centre to a U-form, and bent inversely on both sides, so

312

Paraffin Oil.

as to keep the two extremities horizontal. By one of
these extremities the tube was in communication, by
means of a small copper cock, with a system of columns
and tubes furnished with all the agents usually employed
for freeing the air from foreign bodies; by the other it
was connected with a Liebig's apparatus for retaining
the water and carbonic acid disengaged by the combus-
tion of an organic matter. Finally, the apparatus com-
municated with an exhauster by the intervention of a
flask or of a drying tube, to prevent contact of the humid
air of the exhauster with the air of the apparatus.
To sum up, the apparatus is composed of the following
parts:-

V, an aspirator, serving to circulate air through the apparatus and to pass the disengaged water and carbonic acid over the bodies destined to absorb them.

A, a system of gauges and tubes furnished with agents necessary for the purification of the air.

B, a combustion tube containing the bichromate and the substance to be analysed.

C, a complete system of tubes for the total absorption of the water and carbonic acid.

D, a tube of U-form midway between the exhauster and Liebig's potash tube, and intended to prevent the

access of moist air.

Thanks to these arrangements, it is possible, as will be seen, to regulate at will an operation of which the results leave little to be desired, if some precautions to be described further on are not neglected.

Method of Operating.—In operating upon a carbonate, it is sufficient to introduce into the tube B 30, 40, 50, or 60 grammes of melted potassic bichromate, previously mixed with 1, 2, or 3 grammes of carbonate, if this is insoluble, but if it is soluble the preliminary mixture is superfluous. The tube B being securely connected at its two extremities with the two systems described, we determine the flow of water in the aspirator V, in order to produce a current of air in the apparatus, and then we heat the tube B. Simultaneously with the fusion of the bichromate the disengagement of carbonic acid begins, which is easily moderated during the whole of the experiment. The operation is at an end when the whole mass is fused. The increase of weight of the potash tubes indicate the amount of carbonic acid disengaged, from which the proportion of carbonate is to be deducted. In operating upon a hydrate or upon a mixture of hydrate and carbonate, we proceed in the same manner, only it is necessary to take all precautions, both before and after the operation, that no moisture exists in the tube B. Then the respective weights of the water and carbonic acid show the relative proportions of carbonate and hydrate, taking into account the fact that mixtures of commercial alkaline carbonates and hydrates are always formed of a bihydrate. This result is attributable

Before being used the bichromate should be carefully heated. When cold it should be placed in a bottle stopped with emery, as it absorbs and fixes the aminonia of the air. Notwithstanding the fusion to which the bichromate is submitted, we take the precaution of again melting, just before using it, the quantity required for an operation.

+ In operating on insoluble carbonates, such as those of lime, baryta, strontia, magnesia, manganese, iron, zinc, copper, lead, &c., it is essential, in the first instance, to reduce these salts to a fine powder, by one or other of the methods usually employed for that purpose. When, on the contrary, carbonates, with potash, soda, or lithia bases, especially the two first, are operated upon, this precaution is not only useless, but dangerous, no account of the rapid decomposition which takes place, occasioning projections of bichromate, sometimes reaching as far as the first Liebig's tube, if the precaution is omitted of placing at the anterior part of the tube B a piece of ignited amianthus, which has the effect of retaining the projected portions of bichromate, The operation finished, that part of the and thus preventing errors. tube containing the amianthus should be heated, so as to expel any water which may have condensed in it.

CHEMICAL NEWS,
June 7, 1862.

to the custom of manufacturers of submitting these mixtures to simple aqueous fusion instead of making them red hot. However, by estimating the base common to the water and carbonic acid all uncertainty disappears. For commercial potash and soda, containing sulphides, sulphites, lime, &c., we use the same processes as with carbonates and hydrates, it being only necessary to know how to raise the proportion of bichromate, and, according to the nature of the salt, to observe certain precautions. For the rest we cannot give a better proof of this than by citing some of the results of our experiments.

Having at our disposal a commercial soda-a mixture of carbonate, bihydrate, chloride, and sulphate-of which we knew, besides the alkalimetric standard, the exact proportion of each of the principal ingredients, we selected it on account of its complex nature as the basis of our operations. Submitted to the action of bichroCarbonic acid mate in our apparatus, it yielded— Water

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29 per cent.
5'5 99

These numbers given in sodic carbonate and bihydrate
metric standard of this product.
correspond within a few thousandths with the alkali-
We treated it in the same manner, but with the addi-
tion-

Of
I. 50 per cent. its weight of sulphate of lime; we
collected-

Carbonic acid
Water

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29.5 per cent.
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2. Of 5 per cent. its weight of sulphate of soda containing carbonate; we collected

Carbonic acid

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29.8 per cent.

(The salt not having been dried, the water was not taken into consideration.)

3. Of 100 per cent. its weight of commercial quick lime, containing water and carbonic acid, we collected—

Carbonic acid

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312 per cent. We must not forget that the compounds used in these experiments are with difficulty kept from contact with the air, from which they rapidly absorb water and carbonic acid, which accounts for any difference in the results. Nevertheless, the numbers obtained prove that in circumstances as exceptional as those under which we operated, and where alkalimetric testing was impossible, our results are not far from exact.-Journal de Pharmacie et de Chemie.

TECHNICAL CHEMISTRY.

Paraffin Oil: Report on the Quality of Illuminating
Oils sold in Manchester and the Neighbourhood, by
CHARLES O'NEILL, F.C.S.

IN compliance with a request of the General Committee of
the Manchester and Salford Sanitary Association, I have
examined a number of samples of oils sold in this town
and neighbourhood. In all I have examined thirty-two
samples, twenty-five of which were bought at as many
different retail shops. Two samples of paraffin oil I
obtained direct from the Paraffin Light Company's
premises; and five samples of oil, obtained from London,

1 In operating upon crude potashes and sodas containing charcoal, besides the sulphides and oxisulphides, it is indispensable previously to wash them, to evaporate the washings, and then to determine the weight of the saline inatters thus obtained; the salt being properly dried, it is then only that the bichromate can react.

NEWS

Liverpool, and Bradford, were forwarded to me by the Paraffin Light Company, and included in my examination. Out of the twenty-five samples purchased in Manchester, sixteen were clearly identical with the genuine samples of paraffin oil supplied to me by the Manchester agency, the other nine samples consisted of other kinds of oil differing from the paraffin oil and from one another. Some of them were supplied in answer to a request for paraffin oil; three or four purported to be American rock oils, and were sold under the names of petrolene, kerosene, and photogene. The whole nine were doubtless various qualities of American rock oils, and, adding to these the five samples sent by the Paraffin Light Company, I had fourteen samples from the new and extraordinary oil wells in Pennsylvania and Canada; the remaining eighteen samples being the home manufactured oil sold as "Young's Patent Paraffin Oil."

I obtained three of the lamps employed for burning these oils; they were low-priced lamps, such as are used in the poorest sort of houses, but do not appear to differ in any essential point of construction from the more expensive lamps. These lamps are constructed purposely for burning the paraffin oil; they are not suitable for burning the older kinds of lamp oil, nor are they safe with very volatile fluids, as naphtha and camphine. In deciding whether any of the samples under investigation were dangerous or not, I have considered them entirely in reference to the lamp in which they are used; some of the oils called dangerous might be safely used in another kind of lamp, and the safest of them would be dangerous if used in a moderator or Carcel lamp.

It results, from my experiments, that the chances of accident from the use of these oils may be referred almost exclusively to their greater or less proneness to form an explosive mixture with the air contained in a partly filled bottle or lamp reservoir. I believe it will be found that nearly all the accidents arising from the use of the new illuminating oils have been primarily caused by the ignition of the explosive mixture of combustible vapour and air, either in the bottle in which the stock of oil is kept, or in the reservoir of the lamp; very few accidents happen while the lamp is burning, they nearly all occur while pouring out the oil, or in lighting or trimming the lamp. The explosion may break the vessel and scatter the oil about, and if it be very inflammable in an ignited state.

My examination was then chiefly directed to ascertain whether any of the oils would form an explosive mixture with air at the medium temperature of 60° F.; this temperature may represent the average temperature of domestic rooms where the bottles of oil are kept. To ascertain this point, about a quarter of an ounce of the oil was put into a six-ounce stoppered bottle, the stopper inserted, and the bottle shaken and moved about so as to facilitate the escape of vapour from the oil; in three or four minutes the stopper was taken out and a lighted match held to the mouth of the bottle: if there was a rush of pale blue light through the bottle, the oil was said to give off an explosive vapour at the ordinary temperature, and to be highly dangerous; only two samples out of the thirty-two exploded at a temperature of 60°, numbers one and three, from London and Liverpool respectively. But this temperature can only be considered as the lowest limit of possible danger, the actual limit of danger is the highest temperature to which, under all ordinary circumstances, the oil is likely to be exposed, either in storing or while burning in the

lamp. I concluded from my experiments that a temperature of from 85° to 90° might be calculated upon as often existing in the cistern of a lamp, this high temperature being produced by a long-continued burning of the lamp in a warm room, and on a table near the fire. Any oil, therefore, giving off a combustible vapour and forming an explosive mixture with air at this temperature must be looked upon as unsafe for ordinary use. I tested the remaining thirty samples, and found three which gave an explosive mixture at 85° F. These are numbers four, five, and sixteen, bought respectively in Liverpool, Bradford, Hulme, and Manchester. There are, therefore, five samples really dangerous, and which would require the constant exercise of care and skill to prevent serious accidents. In order to classify the remaining oils, I submitted the whole of them to a temperature of 100° F., and found four of them to yield an explosive mixture at this temperature,-viz., numbers two, nine, eleven, and twelve; three of these were purchased in Manchester. These oils would be highly dangerous if used in any situation where the temperature was as high as roo°; and, though I consider them as unsafe oils, I cannot call them highly dangerous, because the temperature of 100° is hardly ever reached in this climate, and never in the night when lights are required.

As a next step, I exposed the whole of the remaining oils to a temperature of 120° F., testing the explosibility of the vapour; three samples proved explosive at this temperature,-viz., numbers twenty-one, twenty-five, and twenty-eight, purchased in Salford, Hulme, and Manchester. This temperature seems too high to be reached under any ordinary circumstances in a lamp, and I should consider them as ordinarily safe oils. I submitted the remaining twenty samples to a temperature of 150° F., and found that every one yielded an explosive mixture at that temperature; but this I consider beyond the limits of possible danger, and I consider these twenty as very safe oils.

Of the twenty samples which could not be made to explode at 120°, two were American rock oils, and eighteen were Young's paraffin oils; the whole of Young's paraffin oils tested were safe oils. Out of the twelve samples which exploded at or below 120° all were American oils, seven of which were purchased in this neighbourhood.

To recapitulate: Out of thirty-two samples I consider I found twenty quite safe, three less safe but not really dangerous, and nine too dangerous to be used for domestic purposes; four only of the dangerous oils were purchased in Manchester. Out of fourteen samples of American oil, two were as safe as paraffin oil, three less safe but not dangerous, and nine are to be looked upon as dangerous.

In addition to the explosive method of testing, I have tried the liability of the various samples to burst into flame upon contact with a lighted body. I find this inflammability is in close, if not in exact relation with the explosibility; but from various reasons I do not consider it as good a method of testing. I find none of the samples of Young's paraffin oil to take fire at 130°; out of fourteen samples of American oil eleven inflame at this temperature, and three do not. When the oils are scattered upon linen or woollen rags, at the natural temperature of the air, they burst into violent flame upon the most momentary contact with a lighted match or candle; in this, the most dangerous property of these oils, there is no considerable difference between the best and the worst samples of the American and paraffin oils.

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