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THE CHEMICAL NEWS.

VOLUME CXVIII.

EDITED BY SIR WILLIAM CROOKES, O.M., D.Sc., F.R.S., &c.

No. 3064.-JANUARY 3, 1919.

THE PREPARATION OF ORGANIC STANNO - tion of the double salts of the resulting amines appears to

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THE only reference in the literature to double haloids of tin and aliphatic amines that has been traced is a paper by Cook (Am. Chem. Fourn., 1899, xxii., 435), in which the preparation and analyses of the double salts of stannous and stannic bromides and chlorides with the corresponding haloids of the methylamines and ethyl- and triethylamines are described.

The double salts obtained with stannous chloride he terms chlorostannites, and similarly those derived from stannic chloride he refers to as chlorostannates. In order to indicate the molecular proportions of amine and metal numerical ratios are prefixed; thus, the substance 2(CH3)2NH.SnCl4.2HCI is described as 2: 1-dimethylamine chlorostannate. It was thought to be more convenient to regard the salts containing bivalent tin as stannochlorides and those containing quadrivalent tin as stannichlorides. The former compounds may be considered the salts of the (unknown) acid, H2SnCl4 or HSnCl3, and the latter as salts of the acid H2SnC'6. Engels (Comptes Rendus, 1886, ciii., 213) has isolated the latter acid with six molecules of water of crystallisation, analogous to chloroplatinic acid, H2PIC'6 6H2O. But no acid derived from stannous chloride appears to have been prepared, although from conductivity experiments S. W. Young (Fourn. Am. Chem. Soc., 1901, xxiii., 21) inclines to the opinion that HS C3 or H2SnC4 exists in solution. The amine stannichlorides are analogous to the platinichlorides ; thus, methylamine stannichloride, (CH3NH2)2, H2SnCl6, is analogous to the platinichloride, (CH3.NH2)2H2P.C'6.

Cook (loc. cit.) prepared the aliphatic amine stannochlorides by mixing solutions of the amine hydrochloride and stannous chloride. The stannichlorides were similarly obtained, using solutions of stannic chloride. His preparations have been successfully repeated, and in addition the diethylamine salts have been isolated and examined.

constitute a general reaction. Thus it has been found possible to prepare the stannochlorides of methylamine, ethylamine, and certain other amines with an aromatic nucleus by the reduction of the corresponding nitriles with metallic tin. The reaction is expressed by the following typical equation for the conversion of acetonitrile into ethylamine stannochloride :

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CH3.CN+2Sn+5HCI C2H5.NH2,HSnCl3+ SnCl2. as is represented by the equation :— With stannous chloride the nitriles yield stannichlorides 2CH3 CN+4SnCl2+10HCl=

(C2H5.NH2)2, H2SnC6+3SnCl4. Stannochlorides can frequently be converted into the stannichlorides by chlorination, either by slowly passing the gas into a solution of the stannochloride in dilute hydrochloric acid or by slowly adding chlorine water to a concentrated solution of the salt of bivalent tin. In some cases addition of chlorine only is evolved, as, for instance, with the diethylamine salts. The change may be expressed :—

(Et2NH)2, H2SnCl,+Cl2 = (Et2NH)2, H2SnC6.

But in other cases the reaction is a little more complex, and afterwards a portion of the tin in solution is present as uncombined stannic chloride. An illustration of this is afforded by the methylamine salts:2CH3.NH2, HSnC!3+2Cl2 = (CH3.NH2)2, H2SnCl6+SnCl4.

Consequently, in the conversion of salts of the type BHSnCl3 into stannichlorides B2H2SnC6, when oxidation was complete (which was ascertained by withdrawing a few drops of the solution and adding mercuric chloride) solution which gives a precipitate with stannous compounds, a quantity of amine sufficient to combine with the free stannic chloride was added in most experiments. As might be expected this addition doubled the yield of

stannichloride.

Methylamine Stannochloride, CH3.NH2,HSnCl3. Methylamine hydrochloride (2.25 grms.) and crystalline stannous chloride (7.23 grms.) were dissolved together in Methylamine stannochloride was also produced by the 80 cc. of dilute hydrochloric acid (one part of concentrated reduction of hydrogen cyanide with tin and hydrochloric acid to three parts of water). The solution was conacid, and the stannichloride has resulted from the reduc-centrated slightly on a water-bath, and on cooling tion with stannous chloride, but in neither case was the deposited a mass of hair-like silky crystals, which were reaction quantitative. The melting points and composi- filtered off, washed with a little cold dilute bydrochloric tion of the salts prepared in this way were identical with acid, drained, and dried on a porous plate. This salt was those obtained from the amine hydrochloride and the much less soluble in water and dilute acid than either of chlorides of tin. The reduction of nitriles by tin or the constituent chlorides. It did not melt when heated to stannous chloride and hydrochloric acid with the forma a temperature of 305°.

When twice the above proportion of amine hydrochloride was used the crystals formed were identical with those prepared from the constituent salts in the molecular ratio I: I.

Methylamine stannochloride has also been obtained by reducing 1 grm. of hydrocyanic acid with 10 grms. of tin and 100 cc. of concentrated hydrochloric acid diluted with 50 cc. of water in a round flask fitted with a reflux con

0'5143 grm. gave 0.8171 grm. AgCI; Cl=39`29 per

cent.

C2H5NH2,HSnCl, requires Sn=43'77 and Cl = 39°29 per cent.

Ethylamine Stannichloride, (C2H5NH2). H2SлC'6. Five grms. of the stannochloride, dissolved in 50 cc. of dilute hydrochloric acid, were submitted to the action of

a slow stream of chlorine for an hour. Small crystals of the stannichloride, melting at 180°, separated out after concentration and cooling.

denser. The contents of the flask were gently warmed until the tin had completely dissolved. On cooling, a small crop of crystals (about o 8 grm.) separated out, and were found to be identical with those described above. A When 7 grms. of stannic chloride and 16 grms. of second crop was obtained by concentrating the mother-ethylamine hydrochloride were dissolved in 60 cc. of dilute liquor, but was found to be less pure.

When some of this salt was warmed with caustic soda solution an inflammable and alkaline gas was evolved (methylamine). On analysis

0'4732 grm. gave '7906 grm. AgCl; Cl=41'34 per

cent.

03035 grm. gave o‘1777 grm. SnO2; Sn = 46.14 per

cent.

CH3NH2,HSnCl3 requires Cl-4135 and Sn=46:42 per

cent.

Methylamine Stannichloride, (CH3.NH2)2.H2SnCl6.

Five grms. of the above stannochloride were dissolved in 50 cc. of dilute hydrochloric acid, and chlorine was slowly passed in for two hours, when the solution no longer gave a precipitate with a solution of mercurio chloride. It was concentrated on a water-bath and deposited crystals on cooling. These were collected and dried between sheets of bibulous paper. On heating they began to darken at 208°, but did not actually melt up to 305°. They dissolved in cold water to a clear solution which hydrolysed on keeping. It the aqueous solution was warmed immediate hydrolysis ensued.

This salt has also been obtained from methylamine hydrochloride (2·65 grms.) and crystalline stannic chloride, SnCl4,5H2O (7 gims.), which were dissolved together in 80 cc. of dilute hydrochloric acid by warming. The solu tion was concentrated a little, and on cooling it deposited crystals possessing the same properties and composition as those prepared by the other methods.

For the preparation of the salt from hydrogen cyanide a solution containing o6 grm. of this was treated with 9 grms. of stannous chloride dissolved in 80 cc. of dilute hydrochloric acid. The mixture was warmed in a flask fitted with a reflux condenser for an hour. The solution was then transferred to a basin and concentrated on a water-bath. When cooled the concentrated solution deposited crystals of methylamine stannichloride. On analysis

o'5772 grm. gave 02213 grm. SnO2; Sn=30°20 per

cent.

0·2309 grm. gave 0'5001 grm. AgCl; Cl=53.60 per

cent.

(CH3.NH2)2, H2SnCl6 requires Sn30 05 and Cl = 53'72

per cent.

Ethylamine Stannochloride, C2H5NH2,HSṇCl3. Ethylamine hydrochloride (2 grms.) and stannous chloride (5 grms.) were dissolved by warming with 50 cc. of dilute hydrochloric acid, and on slightly concentrating the solution and allowing it to cool long colourless needles separated. When heated they melted at 149°; they dissolved in dilute acids to clear solutions, but in water the salt was slightly bydrolysed.

Crystals, identical with the above in composition and properties and having the same m.p., were obtained by warming acetonitrile (1:25 grms.) with tin (7 grms.) and concentrated hydrochloric acid (50 cc.) until the metal had dissolved. On analysis

0'3425 grm. gave o 1886 grm. SnO2; Sn-43'62 per

cent.

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Dimethylamine Stannichloride, (Me2NH)2 H2SnCl6.

Chlorine water was added slowly from a burette into 25 cc. of dilute hydrochloric acid containing 5 grms. of the above stannochloride, until the solution no longer gave a precipitate with mercuric chloride solution. For this purpose 180 cc. of the chlorine water were required. Concentration to small bulk caused very pale pink almost melted at 289°. colourless crystals to separate on cooling. The salt

tion (30 cc.) of 17 grms. of dimethylamine and 3'7 grms.

Similar crystals resulted from a hydrochloric acid solu.

of stannic chloride. On analysis

0.2879 grm. gave 0'1020 grm. SnO2; Sn=27'90 per

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CHEMICAL NEWS,! Jan. 3, 1919

Determining Composition of Mixtures of Salts of Two Metals.

09852 grm. gave 0·3640 grm. SnO2; Sn=29'11 per

cent.

0'5950 grm. gave 0.8355 grm. AgCl; Cl=34'75 per

cent.

(Et2NH)2, H2SnCl4 requires Sn=29'04 and Cl-34'69 per cent.

Diethylamine Stannichloride (Et2NH)2, H2SnClg.

Four grms. of diethylamine stannochloride were dissolved in 50 cc. of dilute hydrochloric acid and treated with chlorine for one and a-half hours. Crystals were obtained on evaporation to small bulk, and were filtered off on a Büchner funnel at the pump, and finally dried on a porous plate in a desiccator as they were slightly deliquescent. They began to melt with decomposition at about 260°.

Long colourless transparent crystals of this salt, identical with those obtained above, have been prepared from 4'7 grms. of the base and 117 grms. of stannic chloride dis solved together in 100 cc. of dilute hydrochloric acid. They also began to melt and decompose at 260°. analysis

On

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Triethylamine Stannichloride, (Et3N)2,H2SnC/6. The stannochloride of this base has not been isolated pure. Hydrochloric acid solutions containing amine and stannous chloride did not crystallise unless very concentrated, and the mass of crystals so obtained did not give satisfactory analytical results. In most cases the product undoubtedly contained some stannichloride since the precipitate with hydrogen sulphide was yellowish.

The stannichloride was prepared from 2 grms. of the base and 3.5 grms. of stannic chloride dissolved in 50 cc. of dilute bydrochloric acid, as colourless transparent short prisms easily soluble in cold water, producing a clear solution. It melted with decomposition at 268°.

3

When solutions of stannous and amine chlorides were left exposed to air for some days, or were submitted to the action of chlorine, they oxidised, and, on concentration, gave more or less impure crystals of the stannichloride. On analysis

o'5799 grm. gave о'1619 grm. SnO2; Sn=21.98 per

cent.

03266 gım. gave 0'5355 grm. AgCl; Cl-40'13 per

cent.

(Et3N)2, H2SnCl6 requires Sn=22°33 and Cl = 39.86 per cent.

A METHOD FOR DETERMINING THE COMPOSITION OF A MIXTURE OF SIMILAR SALTS OF TWO METALS, WITHOUT SEPARATING THE MIXTURE INTO ITS

CONSTITUENTS.

By H. N. WILSON.

two very similar metals in a mixture, and in many cases It is often necessary in analysis to find the quantities of employed is often expensive. In the first class may be the metals are difficult to separate, and the method to be placed mixtures of strontium and barium, or antimony and arsenic, and in the second mixtures of sodium and potassium. In all such cases an arithmetical method would be vastly useful and time saving.

Such a method has been discovered in the course of in

vestigations on potassium, and it is proposed to show how it may be used to advantage in this and other cases.

For determining potassium apart from sodium without using perchloric acid or platinic tetrachloride it is first of all necessary to obtain a mixture of the chlorides free from impurity and then to estimate the percentage of chlorine. Then by the means shown below the two constituents may be calculated.

The atomic weights are:-K, 39'10; Na, 23'00; and Cl, 35'45. From these we know that pure potassium chloride contains 47'5519 per cent of chlorine, and sodium chlorine 60.6501 per cent of chlorine.

These two cases (0'00 per cent NaCl and 100'00 per cent NaCl) may be taken as the limits of a mixture of the two salts, and so the limiting percentages of chlorine are respectively 47:5519 and 60 6501, as shown in the graph appended, which shows the rise in Cl as the sodium

chloride increases.

It will thus be seen that while the percentage of chlorine rises 13 0982, the percentage of sodium chloride rises 100'00, so when the percentage of chlorine rises 100 the percentage of NaCl rises = 7·6346.

100'00

13.0982

So if we subtract the minimum possible percentage of chlorine in the mixture from the percentage found in the sample under examination, and multiply the result by 7.6346 we obtain the exact percentage of sodium chloride in the mixture, and from this the percentage of potassium chloride or of metallic potassium can easily be obtained.

Example.-A given mixture of sodium and potassium chloride shows 50'5061 per cent Cl, how much potassium is present? Now, 50.5061-47'5519=2.0982, and 2.0982 x 7.6346 19 1491, which is the percentage of sodium chloride in the mixture.

... The percentage of KCl is 80-8509.

... The percentage of metallic potassium is 43'3812. A case in which the above method would be useful is in the determination of total alkali in flue dust; in this case the soluble portion would have to be extracted, and all other metals and sulphates precipitated by the usual means, which will give in solution a mixture of ammonium compounds, and K and Na salts which are broken down by heating into carbonates, &c., which dissolve in HCl to form chlorides, from which the estimation is easy.

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