XXI.-On Picric Ether.

By H. MÜLLER, PhD., and J. STENHOUSE, LL.D., F.R.S.

PROFESSOR MITSCHERLICH✶ believed that he had produced this compound by digesting for some hours a solution of picric acid in absolute alcohol mixed with a little sulphuric acid. This experiment has been repeated by Erdmann and several other chemists, but without success, a quantity of resinified picric acid being the only product. This result agrees with the description that Mitscherlich gives of his product, but which he did not analyse.

Picric ether may, however, be readily produced by acting on picrate of silver with iodide of ethyl.

One of the most convenient ways of preparing picrate of silver is to add an excess of carbonate of silver to a hot solution of picric acid, and after boiling for a few minutes, filter the solution and leave it to cool, when the picrate crystallises out in beautiful shining yellow needles, united in radiated groups.

One part of this salt in a perfectly dry state is placed in a flask furnished with a long condensing tube, and five parts by weight of iodide of ethyl are then poured on it. By using this large excess of iodide of ethyl, viz., ten times the theoretical quantity, the liquid does not become very hot, thus avoiding the loss of iodide of ethyl which takes place if equal weights are used, the action then being very violent. After allowing it to stand for a short time, it is digested in a water-bath for five or ten minutes to complete the decomposition, and the digesting tube being then replaced by a short bent one, the excess of iodide of ethyl is distilled off.

To the residue in the flask, consisting of iodide of silver and picrate of ethyl, 8 parts of spirit are added, and the whole is boiled for a few minutes and filtered; on cooling, the solution deposits the picric ether in long needles. By again treating the residue with spirit, a further amount of the ether may be extracted The entire product is recrystallised once or twice from spirit and well washed with distilled water, in order to separate the small quantity of picric acid which adheres to it.

If an alcoholic solution of iodide of ethyl be used instead of the pure iodide in the preparation of picrate of ethyl, a large propor tion of picric acid is set free, and at the same time some ethylic

Lehrbuch. der Chemie i, 222.

ether is formed. In order to obtain the picric ether from this mixture, the solution is filtered from the iodide of silver, and, after evaporation, boiled with water, into which enough carbonate of calcium is gradually introduced to saturate the free picric acid. The picric ether separates in the form of a heavy oil, which congeals on cooling, and may be purified in the way already described. The first process already given is, however, by far the best.

Picric ether, when purified in the way described, consists of nearly colourless needles, having only a slight yellow tinge, which, when slowly deposited from spirituous solutions, are readily obtained one or two inches in length. When exposed to light they gradually become coloured. It is slightly soluble in boiling water, from which it crystallises out entirely on cooling. It is likewise soluble in iodide of ethyl, ether, bisulphide of carbon, and benzol. It melts at 78°.5 C., and congeals at 73° C. When heated on platinum foil, it burns with a smoky flame. But when heated in a tube, it melts, and, on increasing the heat, is decomposed, with slight deflagration and deposition of carbon.

The substance dried in vacuo was analysed with the following results:

I. 410 grm. gave 561 grm. carbonic acid, and 120 grm. water. II. 535

733

•133

These numbers, as may be observed, agree very closely with the formula CN,O,H2.C2H5.

XXII.-Styphnic or Oxypicric Ether.

By JOHN STEN HOUSE, LL.D., F.R.S.
STENHOUSE,

THE styphnic acid which I employed for the preparation of this compound was obtained by treating with nitric acid the concen. trated extract of sapan wood, which is largely manufactured for the use of calico printers. In preparing the acid from sapan

wood extract, I have found the following to be the best mode of proceeding.

20 measures of nitric acid, of sp. gr. 1.36, are heated in a large retort connected with a good condensing arrangement, 120 parts of the concentrated aqueous extract are gradually added, and the whole is digested for three or four hours, pouring back the weak acid that distils over.

The yellow solution thus obtained is first evaporated down over a bare flame, and then over a water-bath, until it becomes of the consistence of a thick syrup.

This syrup is gradually added to 4 measures of nitric acid, sp. gr. 1.45, previously heated to the boiling-point in a retort, 4 parts more acid being used to wash out the evaporating dish; the whole is then digested for four or five hours; about 3 parts of the acid are distilled off; the residue in the retort is transferred to a beaker, the retort being washed out with a little cold water (about 4 parts); the liquor is decanted from the sandy styphnic acid; 4 parts more water are added; the whole is well stirred; the liquid again decanted, and the crude styphnic acid is thrown upon a filter to drain. The washings, when evaporated over the water-bath and again digested with nitric acid, yield a small additional quantity of styphnic acid.

The crude styphnic acid obtained by the above process is placed in a flask with about 16 parts water, and, when boiling, a concentrated solution of carbonate of potassium is gradually added. When about one-half the proper quantity of carbonate of potassium solution has been poured in, the styphnic acid dissolves completely, but on the addition of more of the solution, a considerable quantity of styphnate of potassium is precipitated. As soon as it exhibits a decidedly alkaline reaction, the whole is boiled for a few minutes and allowed to cool, when the styphnate of potassium crystallises out. This is thrown on a filter and washed with a small quantity of cold water. After one or two recrystallisations, the potassium-salt is obtained in a perfectly pure state.

By treating a hot solution of the potassium-salt with nitric acid, perfectly pure styphnic acid may readily be procured.

Action of Chlorine on Styphnic Acid.

When styphnic acid is added to a cold solution of hypochlorite of calcium, chloropicrin is evolved. In this respect it closely resembles picric acid; but on the application of heat, the whole

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of the styphnic acid is decomposed, chloropicrin and carbonic acid being the sole products.

When styphnic acid is heated for some time with hydrochloric acid and chlorate of potassium, it is completely decomposed, yielding chloropicrin, but not a trace of chloranil. When picric acid is similarly treated, it produces, as is well known, both chloranil and chloropicriu.

As styphnic acid, therefore, is incapable of yielding chloranil, and as the products of the action of reducing agents are so different from those of picric acid, styphnic acid is not, as Erdmann erroneously supposed, merely oxidated picric acid, but it must have a different nucleus entirely unconnected with that of picric acid.

Styphnic Ether.

The styphnate of silver used in the preparation of this ether was obtained from the potassium-salt, by dissolving it in about 20 to 25 parts of hot water, and precipitating by a slight excess of nitrate of silver, washing well with cold water, in which it is but slightly soluble, and drying at a moderate temperature. The styphnate of silver thus obtained is placed in a flask furnished with a long condensing tube, and 5 parts of iodide of ethyl are poured on it; the reaction is completed by heating it for five to ten minutes in a water-bath. When cold, the condensing tube is replaced by a short bent one and the excess of iodide of ethyl is distilled off. The residue is then treated with hot spirit, which extracts the styphnic ether and deposits it on cooling in large crystals. After two or three recrystallisations out of hot spirit, it is obtained in a state of perfect purity. This ether crystallises in the form of long laminæ, which are nearly colourless when first prepared, but rapidly become orange-brown on exposure to light. It melts at 120°5, and when exposed to a higher temperature, volatilizes, but at the same time undergoes partial decomposition. When heated on platinum-foil, it burns with a bright flame, but without deflagration. It is soluble in alcohol and ether, and still more so in benzol, slightly soluble in bisulphide of carbon, and insoluble in water. When heated with solution of potash, it is decomposed, with production of styphnate of potassium and alcohol.

The following are the results of the analysis of the substance dried in vacuo :

I. 436 grms. substance gave 637 grms. carbonic acid, and 146 grms. water.

II. 354 grms. substance gave 517 grms. carbonic acid, and 121 grms. water.

I have likewise obtained chrysammic ether by treating chr ysammate of silver with iodide of ethyl. It crystallises in needles. I hope shortly to publish the analysis and description of this substance. The analyses were made for me by my assistant, Mr. Charles Edward Groves.

XXIII.-The Water Supply of the Metropolis during the Year 1865-66.

By E. FRANKLAND, F.R.S.

[Abstracted from the Annual Report to the Registrar-General.]

THE following are the results obtained in the monthly analyses of the metropolitan waters, during the year commencing February, 1865, and ending January, 1866* :

The analytical determinations are conducted as follows:-1000 cubic centimetres of the water are evaporated in a weighed platinum dish on the water-bath, an accurately measured quantity of a solution of sodic carbonate of known strength having been previously added. The solution used contains 10 grammes of pure * The analyses in the early part of the year were made by Dr. A. W. Hofmann.