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For, out of the data here given we may construct two equations. Taking a for the number of equivalents of palmitine, and y for that of the oleine present in the tallow, and equating the carbon ratios of the three substances, as the least liable to error, we have

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This is sufficient to prove that the numbers obtained by analysis of the tallow are compatible with, and, in fact, are explained with great simplicity by the view that this body contains only palmitine and oleine.

Nevertheless, it appeared interesting to ascertain that the oleic acid. present in the tallow was of the ordinary formula, and my assistant, Dr. Ewald, undertook the investigation of it.

A portion of the tallow was saponified; the acids were then separated by hydrochloric acid, melted at a low temperature, mixed with alcohol, and cooled. The solidified mass was very strongly pressed; the fluid expressed was diluted with alcohol, quickly filtered, and precipitated by basic acetate of lead. The precipitate, after washing by alcohol and separation of the alcohol by pressure, was rapidly dried over sulphuric acid in vacuo. The dried and pulverised salt was then exhausted by cold ether, which takes up the oleate of lead only. The solution is decanted from the residue, and decomposed by dilute hydrochloric acid in a stoppered glass cylinder, without access of the air.

The chloride of lead rapidly subsides, leaving the clear yellow solution of oleic acid in the ether. This solution is now distilled from another flask by a gentle heat, in the water-bath, to separate the ether, and the residue dissolved in alcohol. From this solution the oleic acid is precipitated, by the addition of ammonia in slight excess and chloride of barium, as the pure oleate of baryta. It is quite white, settles quickly, and is filtered and washed with ether. This washing with ether, according to Heintz, at once protects the precipitate from the air, and dissolves a salt containing more baryta than the neutral oleate.

The salt so prepared is quickly pressed and dried in vacuo, and finally in an air-bath at 50° to 60°. It was burnt with oxide of copper and chlorate of potash.

I. 0.4678 grm. yielded 1.0636 carbonic acid (made up of 1.0342 in the potash apparatus +0.0294 absorbed by the baryta to form 0.1317 of carbonate of baryta), and 0.4056 water.

II. 0.6364 grm. yielded 0.2122 BaO, SO,=0·1393 BaO.

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II.—On the Absorption of Chlorine in Water.

By HENRY E. Roscoe, B.A., PH.D.

Ar the beginning of this century, Dalton and Henry set up the hypothesis, that the amounts of gas dissolved by a liquid vary as the pressure under which the absorption takes place. As, however, this relation between the absorbed gas and the pressure could not be deduced from Dalton and Henry's own experiments, and still less from the later ones of Saussure, it has been regarded by chemists as an ungrounded hypothesis, until Professor Bunsen,* in his late research, showed that it had a foundation in a true law.

A series of very careful experiments which Dr. Carius and Dr. Schönfeld have carried out with the absorptiometer described by Bunsen, not only give fresh proofs of the exactitude of the law, but show beyond doubt that it is applicable to gases of very great solubility.

It thus appears of great interest to examine the absorptiometrical relations of gases at the limits of the temperatures at which the same are capable of entering into chemical combination with the solvent. Dr. Schönfeld has examined sulphurous acid in this respect, and has found that the law is followed even at temperatures which ap

*Phil. Mag., Feb. and March 1855; Ann. Ch. Pharm. xciii. 1.

proach the point where this acid forms a crystalline hydrate with the solvent.

In the following research I shall describe the absorptiometrical relation which exists between chlorine and water at temperatures approaching that at which hydrate of chlorine is formed. As the absorption-coefficient of this gas has already been accurately determined at Schönfeld, I have been able to confine myself to the examination of mixtures of gas of known composition containing chlorine.

The first mixture of gases examined was that evolved by the electrolysis of concentrated hydrochloric acid. The electrolysis was conducted in a small flask of about 100 cubic centimeters' capacity, filled with hydrochloric acid, into which two poles of conducting carbon dipped. A glass tube, with the upper end drawn out, was fastened on to the neck of the flask by means of a caoutchouc ring, and through the tube were melted two platinum wires, which communicated below with the carbon poles and above with the battery. The gas, obtained by a current of four of Bunsen's elements, was washed by passing through a series of bulbs containing water, blown on a glass tube and placed in an oblique position.

The composition of the gas thus obtained by electrolysis must first be determined. For this purpose the gas was dried over fused chloride of calcium, and led into a tube of known capacity, drawn out at both ends, until there could be no doubt that the last traces of atmospheric air were driven out. After accurate observation of the temperature and pressure, the tube filled with the mixture of gas was closed with the necessary precautionary measures, and one end opened under a solution of iodide of potassium; and in order to effect the rise of the liquid, this was done at a lower temperature than that at which the gas was collected. The iodide of potassium was immediately absorbed, and a quantity of iodine, equivalent to the free chlorine present, was separated out.

From this free iodine the amount of chlorine present in the tube was determined by Bunsen's volumetric method.* Two experiments with gas collected at separate occasions gave

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* Ann. Ch. Pharm. lxxxvi. 265; Chem. Soc. Qu. J. vi. 90.

The signification of the various letters will be seen by reference to the original research.

From these numbers the volume of chlorine V reduced to 0° C. and 0.76 pressure of mercury contained in the tubes used in the experiments, is found in cubic centimeters by means of the formula

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in which 0.0031823 is the weight in grms. of 1 cubic centimeter of chlorine at 0° C. and 0.76 pressure of mercury.

The first experiment gave 16.24; the second, 87.36 cub. cent. chlorine at 0° C. and 0.76 pressure of mercury.

If the total capacity of the tube be called C, the barometric pressure at the time of closing P, and the temperature during the same time T, the total volume of gas reduced to 0° C. and 0.76 contained in the tube is found by the following formula :—

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For Experiments (1) and (2) the following values were found :

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This gives the total volume of the first tube 32.58; of the second, 174.65. If, now, the respective volumes of chlorine found by graduation be subtracted from the total volumes, the volume of hydrogen gas present in the mixture will be obtained.

The composition of the two mixtures of gas was, therefore,

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As the liquid subjected to electrolysis only contained hydrochloric acid and water, the products of decomposition formed could only contain chlorine, hydrogen, oxygen, or the oxides of chlorine or hydrogen. The absence of free oxygen can be safely inferred from the experiments just cited, for every volume of oxygen which is set free by the electrolysis of water is necessarily accompanied by two volumes of hydrogen, whilst chlorine and hydrogen are set free in equal volumes by the electrolysis of hydrochloric acid. If, therefore, water were decomposed in the above manner, the analysis would not

have shown equal volumes of chlorine and hydrogen, but an excess of the latter, which, as already stated, was not the case. For the same reason, peroxide of hydrogen cannot be formed in the decomposition, as the presence of this body would cause a still greater proportional excess of hydrogen.

It only remains, therefore, to be shown, that in the mixed gas no oxygen-compounds of chlorine are present. Let us in the first place, to take a particular case, examine if the gas could contain hypochlorous acid. 2 vols. of hypochlorous acid consist of 2 vols. of chlorine and 1 vol. of oxygen; 1 vol. of oxygen is equivalent to 2 vols. of chlorine, and sets free in the volumetric process exactly as much iodine as 2 vols. of chlorine. This process leaves it, therefore, quite undecided whether 4 vols. of chlorine or 2 vols. of hypochlorous acid were present; and further, because in the electrolytic decomposition of 4 vols. of hydrochloric acid, as in electrolytic formation of 2 vols. of hypochlorous acid, exactly the same amount, 4 vols., of hydrogen, must be set free, it is clear that the volumetric process will always show equal volumes of chlorine and hydrogen, whether the gas be rendered impure by the presence of hypochlorous acid or not. The question as to the presence of this latter gas is, however, easily answered, when a direct estimation of chlorine with solution of silver is made together with a volumetric determination. The silver determination shows only the amount of chlorine, and not the oxygen of the hypochlorous acid, and therefore may give only half as large an amount of chlorine as the volumetric process. The two following experiments show that the amount of chlorine found by the volumetric method agrees so exactly with that found by the silver determination, that the absence of hypochlorous acid may be certainly deduced. By similar reasoning, the absence of all other volatile oxides of chlorine can be proved.

Three tubes were filled with the gas as formerly described. The first was opened under iodide of potassium, and analysed by the volumetric process; the two others were opened under tolerably concentrated sulphurous acid, by means of which the whole of the chlorine was reduced to hydrochloric acid and precipitated in presence of excess of nitric acid as chloride of silver.

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