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NH2,HSnCl3

o-Amidobenzoic Acid Stannochloride, C6H4 COOH. o-Nitrobenzoic acid (17 grm.) was warmed in a conical flask with 3.6 grms. of granulated tin and 30 cc. of concentrated hydrochloric acid diluted with an equal volume of water. When all the metal had dissolved the liquid was transferred to a basin, and on cooling deposited a mass of colourless microscopic crystals, which were filtered off, washed with a little dilute hydrochloric acid, drained, and dried on a porous plate in air.

The salt dissolved in cold water, giving a clear acid solution which rapidly hydrolysed, however, on standing, or immediately on gentle warming, unless dilute mineral acid was added. It dissolved in cold alcohol and the solution remained clear on boiling. It was insoluble in chloroform, carbon tetrachloride, toluene, ligroin, and ethyl acetate. On heating, the substance began to soften at 85° and melted completely at 125° to a colourless liquid. The hydrochloric acid solution gave a white precipitate with mercuric chloride solution, and hydrogen sulphide gave the brownish black precipitate of stannous sulphide. o-Amidobenzoic acid stannochloride was also prepared from the component salts. o-Amidobenzoic acid (137 grms.) and stannous chloride (2·26 grms.) were dissolved together in 20 cc. of concentrated hydrochloric acid and 30 cc. of water by heating. On cooling, a mass of very short colourless needles separated. They were identical with the product obtained above. On analysis

1.8144 grms. gave 0.8832 grm. SnO2; Sn -33.18 per cent. 0'5687 grm. gave 0 6703 grm. AgCl; Cl=29'17 per cent. NH2.C6H4.COOH,HSnC13 requires Sn=3279; Cl= 29 37 per cent.

o-Amidobenzoic Acid Stannichloride,
(NH2.C6H4.COOH)2H2SnC16.

The stannochloride (3 grms.) was dissolved in 40 cc. of dilute hydrochloric acid and chlorine was slowly passed through the solution for three hours. At the end of this time the solution gave no precipitate with a solution of mercuric chloride. The solution was concentrated on a water-bath until crystals formed; on cooling, slightly deliquescent needle prisms separated. These were easily soluble in cold water, but the solution readily hydrolysed. They dissolved in alcohol but not in other organic solvents.

The salt was also prepared from mixed solutions of the amido-acid (2.7 grms.) and stannic chloride (3'5 grms.). On analysis both products were found to have the same composition

0.8238 grm. gave 0.2376 grm. SnO2; Sn = 19:34 per cent. 10362 grm. gave 1 4683 grm. AgCl; Cl-35 06 per cent. (NH2.C6H4 COOH)2H2SnCl6 requires Sn = 1960 and Cl- 35 12 per cent,

m-Amidobenzoic Acid Stannochloride, (NH2.C6H4.COOH),H2SпC4.

m-Nitrobenzoic acid (67 grms.) was reduced with 7.2 grms. of tin and 100 cc. of concentrated hydrochloric acid diluted with 50 cc. of water. The mixture was warmed in a conical flask until the metal had dissolved, and was then filtered whilst hot into a basin. When cold a crop of white granular crystals separated. On examination this first crop of crystals was found to be the hydrochloride of m-amidobenzoic acid.

The filtrate was concentrated on a water-bath and on cooling it deposited a feathery mass of fine needle crystals of the stannochloride, easily distinguished from the above granules.

The double salt was also prepared from 1'5 grms. of m-amidobenzoic acid and 2'9 grms. of stannous chloride, dissolved in 50 cc. of dilute hydrochloric acid by warming. A mass of fine needle crystals similar to those obtained above, separated and were isolated and examined. The filtrate also yielded more of the compound on standing.

Crystals obtained by both methods melted at 240°, and were not very soluble in water even when warm. The solution was strongly acid, and boiling did not cause hydrolysis. The salt dissolved readily in warm dilate hydrochloric acid; it was slightly soluble in alcohol, but insoluble in chloroform, toluene, &c. On analysis—

0.6433 grm. gave o 2861 grm. SnO2; Sn=21°42 per cent. 0 2269 grm. gave 0 2403 grm. AgCl; Cl=26 20 per cent. (NH2 C6H4 COOH)2H2SnCl4 requires Sn = 22.11;

Cl 26 43 per cent.

m-Amidobenzoic Stannichloride,

(NH2.C6H4.COOH)2H2SnCl6.

The above stannochloride (4 grms.) dissolved in 50 cc. of dilute bydrochloric acid was submitted to the action of chlorine for two hours until the solution no longer gave the reactions for stannous tin. The solution was concentrated on a water-bath and deposited a small quantity of pale yellow granular crystals on cooling and standing over the week-end.

This substance darkened indefinitely at 220-230° and was found to contain a very low percentage of tin (about 1 per cent). It was a chlorination product. The hydrochloride of m-amidobenzoic acid was also obtained from insufficiently concentrated solutions, in the preparation of the stannichloride by this and other methods.

The second crop of crystals were colourless, short radiating needle masses, entirely distinct from the yellow granules.

The salt dissolved easily and completely in cold water, and the solution could be boiled without showing signs of hydrolysis. On passing hydrogen sulphide through the solution, yellow stannic sulphide was precipitated. It melted at 193°.

The stannichloride was also obtained from m-amidobenzoic acid (2.76 grms.) and stannic chloride (3'57 grms.) dissolved to a clear solution in 50 cc. of dilute hydrochloric acid by warming. This solution deposited a mass of very pale brown short needles, melting at 190-192°.

Almost colourless short needles were obtained from mixed solutions of m-nitrobenzoic acid (3.34 grms.) and stannous chloride (13'5 grms.) in aqueous alcoholic hydrochloric acid. On analysis

11413 grm. gave 0.2921 grm. SnO2; Sn = 20.15 per cent. 11413 grm. gave 19428 grm. AgCI; Cl=35'03 per cent. The above formula requires Sn=19.60; Cl=35'12 per

cent.

p-Amidobenzoic Acid Stannichloride,
(NH2.C6H4.COOH)2H2SnC/6.

p-Amidobenzoic acid (2.76 grms.) and stannic chloride (3'57 grms.) were dissolved together in 70 cc. of dilute hydrochloric acid by warming. Small pale yellow brittle needles separated out on cooling. They were filtered off, drained, dried, and examined.

They dissolved readily in cold water to a clear solution which was strongly acid, and became cloudy when heated. The crystals did not dissolve in organic solvents, and did not melt up to 315°. On analysis-

0.2738 grm. gave 0 0710 grm. SnO2; Sn = 20'51 per cent. 02738 grm. gave o'3957 grm. AgCI; Cl=34'75 per cent. The above formula requires Sn = 1960 and Cl=35 12 per cent.

p-Amidobenzoic acid stannichloride was also obtained by reduction of 16 grms. of p-nitrobenzoic acid (obtained from p-nitrotoluene hy oxidation with potassium permanganate) with 67 grms. of stannous chloride in 100 cc. of dilute hydrochloric acid. The product was identical with that prepared above in analysis and did not melt up to 310°.

Attempts to prepare p-amidobenzoic acid stannochloride unsuccessful. Reduction of p-nitrobenzoic acid with tin and bydrochloric acid yielded a dark solution, which was not decolorised by the use of excess of tin. No crystalline product was isolated in a pure state. The dark amorphous mass left on evaporation to dryness on a waterbath, was washed on a filter-paper with dilute acid. drained, dried in a steam oven, and analysed. It was found to possess a tin-content which varied in different experiments, depending upon the quantity of metal used and the length of washing with acid.

Mixed solutions of p-amidobenzoic acid and stannous chloride in dilute hydrochloric acid on concentration deposited short pale yellow needle prisms, which were devoid of tin, and were those of p-amidobenzoic acid hydrochloride. No pure stannochloride was isolated from

the filtrates.

Sulphanilic Acid Stannichloride, (NH2.C6H4.SO3H)2H2SnC16. Molecular proportions of sulphanilic acid and stannous chloride dissolved in dilute hydrochloric acid did not yield a stannochloride.

Sulphanilic acid (3'46 grms.) and stannic chloride (3'57 grms.) dissolved in 6o cc. of hot dilute hydrochloric acid gave a fine white microcrystalline powder, which was not very soluble in cold water. With warm water metastannic acid separated. The salt did not melt but began to darken and decompose at 270°. On analysis0.7621 grm. gave o 1701 grm. SnO2; Sn = 17'59 per cent. 0.7621 grm. gave 10139 grm. AgCl; Cl=32'90 per cent. Per cent Cl by Stepanow's method = 31.33. (NH2 C6H4.SO3H)2.H2SnCl6 requires Sn=1746 and Cl=31 28.

4-Amidophthalic Acid Stannochloride,
[NH2.C6H3(COOH)2]2H2SnCl4.

4 Nitrophthalic acid (2.3 grms.), prepared according to Miller (Ann., 1881, ccviii., 224), was reduced with tin (4.2 grms.) in 60 cc. of concentrated hydrochloric acid and 60 cc. of water. The mixture was warmed until all the metal had dissolved and was then filtered. A mass of white, very short needles separated cut of the filtrate. It was filtered off, washed with dilute acid, drained, and dried on a porous plate. The salt melted sharply at 274°, and dissolved in cold water. Hot water caused hydrolysis. On analysis-

O'3994 grm. gave o'0944 grm. SnO2; Sn = 18'59 per cent. 03994 grm. gave 0.5806 gtm. AgCl; Cl = 35.96 per cent. The above formula requires Sn=19'00; Cl=34'05 per

cent.

4-Amidophthalic Acid Stannichloride, [NH2.C6H3.(COOH)2]2H2SnC16. Chlorination of the above stannochloride did not yield the stannichloride pure, other changes accompanied the oxidation of stannous salt to stannic.

The stannichloride was obtained from 4-nitrophthalic acid (2 grms.) and stannous chloride (69 grms.) by warming for two hours with 100 cc. of dilute hydrochloric acid.

The reduction of 3-nitrophthalic acid with tin and hydrochloric acid was carried out as for the 4-compound, but the short needle prisms obtained gave no precipitate with mercuric chloride solution, or when hydrogen sulphide was passed into their acid solution. The substance contained chlorine, and when diazotised with nitrous acid and an alkaline solution of B-naphthol was added, it gave a deep red azo-dye.]

Amidosalicylic Acid Stannichloride,
[NH2C6H3(OH)COOH] 2H2SnC16.

Nitrosalicylic acid (prepared according to the method of Hirsch, Ber., 1900, xxxiii., 3238) was reduced with tin prisms, which, however, did not contain tin. When and hydrochloric acid and gave short dark brown needle diazotfsed and treated with an alkaline solution of B-naphthol the product gave a deep red substance.

The reduction of 1 67 grms. of the nitro-acid with 6.78 grms. of stannous chloride was carried out in 30 cc. of strong hydrochloric acid and 30 cc. of alcohol by heating on a water-bath for an hour in a flask fitted with a reflux condenser. The alcohol was evaporated, and the solution deposited small brownish prismatic crystals which melted at 128°. They dissolved in water, but the solution became cloudy on heating. On analysis

O'9354 grm. gave o 2084 grm. SnO2; Sn=17'55 per cent. The above formula requires Sn = 18·56 per cent. o-Nitrocinnamic acid was submitted to the action of tin and of star nous chloride in the presence of hydrochloric acid, but the resulting products were not double tin chlorides.

Glycocoll, the only aliphatic amino-acid employed with a view to preparing the stanno and stanni-chlorides, was dissolved with molecular quantities of stannous and of stannic chlorides in dilute hydrochloric acid. The concentrated solutions did not crystallise even after standing for some months. Experiments were made to see whether the double salts could be thrown out from the syrupy liquid by shaking with alcohol, ether, or benzene, but all

were unsuccessful.

For analysis, a modification of the method mentioned by Pfeiffer (Ann., 1913, cccxcviii., 195) was adopted. The salt was dissolved in a convenient volume of cold water, and an ammonium nitrate solution, containing about the added. To this dilute sodium carbonate solution was same weight of nitrate as of the substance taken, was boiled, and on cooling the precipitate was filtered off, added until the solution was just alkaline. It was then washed, dried, and ignited to stannic oxide and weighed nitric acid and boiled. Addition of silver nitrate solution as such. The filtrate and washings were acidified with precipitated the chloride quantitatively.

CITY AND GUILDS OF LONDON INSTITUTE.-Diplomas of Associate have been awarded by the Council to the following students: In Engineering - J. D. Aguiar, R. H. Barfield, J. A. A. Best, C. Grad, A. G. Griffith, T. J. Griffiths, F. St. A. Hartley, G. H. Hopewell, E. W. A. Janmoulle (Siemens Medal), A. A. de Lemos, K. P. P. Menon, R. B. McC. Potter, J. H. Reyner (Henrici Medal), C. J. H. Trutch, S. Vaughan, A. C. Warren (Henrici Medal), H. C. Wilkinson, E. W. Workman, R. G. P. Wyatt (Bramwell Medal). In Applied Chemistry-E. Fisher, J. R. Fraser, F. D. M. Hocking, S. J. Hopkins, L. Mendel, N. Plotzker, N. Singer, C. E. Spearing, H. G. Tribley, H. B. Williams,

OF LEAD.

By ERNEST NYMAN, Chemical Laboratories, Milton Hersey Co., Ltd., Winnipeg, Man.

As far as the writer knows chemical literature does not mention the property of lead ferrocyanide and lead cxalate of being soluble in ammi acetate solution, neither the possibility of titrating zinc in ammoniacal solu. tion, using uranyl acetate weakly acidified with hydrochloric acid, as outside indicator. Methods based on these facts are outlined in the following, and may prove useful, particularly in determination of zinc, calcium, and lead in paint pigments, where these elements are apt to be present together. In the work the writer has also proved the relation of the zinc salts precipitated by potassium ferrocyanide in acid and ammoniacal solution, and the different factors for zinc in acetic acid solution and in a solution weakly acid with hydrochloric acid.

Determination of Zinc.

To the acid solution of the salts add NH,OH till strongly ammoniacal, then make acid with acetic acid, and if a precipitate still remains, add a few grms. of ammonium acetate, heat to boiling, remove from heat, make faintly ammoniacal, and add some K4Fe(CN)6 solution. The zinc is precipitated as normal zinc ferrocyanide, Zn2Fe(CN)6, the lead remains in solution, lead ferrocyanide being soluble in ammonium acetate. Neither does Ca interfere.

If, when adding NH4OH to an acetate acid solution, no precipitate forms, it may indicate either absence of lead or an amount that is soluble in the ammonium acetate formed.

In this way zinc may be determined qualitatively as above, as well as quantitatively, as follows:

Proceed as above till the faintly ammoniacal solution is obtained, arrange the temperature of the solution to be 70-80° C., add, dropwise, standard K4Fe(CN)6, stirring thoroughly, and spotting the end-point by the usual reddish brown tinge developed with uranyl acetate on a spotplate, the spotting modified, as will be indicated in the following:

This tinge is caused by a faint precipitate of (UO2)2Fe(CN)6. In titrating a weakly acid solution this tinge appears as known, when a drop of the solution comes in contact with a drop of the uranyl acetate solu❘ tion on the spot-plate.

This is not the case when the solution titrated is ammoniacal, because canary-yellow amorphous ammonium uranate is precipitated by the NH4OH. 2UO2(CO2CH3)2+6NH4OH-(NH4)2U2O+

+CH3CO2NH4+3H2O.

No reddish brown tinge is thus developed, also because the (UO2)2Fe(CN)6 possibly formed is soluble in the am

monium uranate :

(UO2)2Fe(CN)6+6NH,OH-(NH4)4Fe(CN)3+

+3120+(NH4)2U2O7. But adding a drop of HCl solution, say (1: 12), to the uranyl acetate drop on the spot-plate before titrating will neutralise any free ammonia, and then the ferrocyanide acts with the acetate forming the reddish brown tinge. Also it must be remembered that in an ammoniacal solution normal zinc ferrocyanide, Zn2Fe(CN)6, is pre

The practical factor as arrived at from determinations (see below) carried on by the writer is 13450. The difference between the factors is satisfactorily small, and is to be attributed to some unavoidable experimental cause, may be, partly, to a difference in sensitiveness of the external indicator to an acid and ammoniacal titration. This being the case, it may be stated that the zinc salts precipitated in ammoniacal and acid solution are identical with the zinc salts of respective formulæ, Zn2Fe(CN)6 and K2Zn3 [Fe(CN)6] 2. This corrects the statement found in the literature on the subject, which states that the zinc salts precipitated are not identical with zinc salts of these formulæ, but fairly closely approach the identity.

From the determinations conducted it also appeared that when titrating an acetic acid zinc solution for standardising the ferrocyanide, a constantly lower value of zinc was obtained than when the titration was carried on in weakly HCl acid solution. But this discrepancy vanished, and identical values were obtained if a drop of HCI was added to the uranyl acetate drop on the spotplate. This shows that a larger excess of K4Fe(CN)6 is needed to give the reddish brown precipitate in an acetic acid solution than in a HCI acid solution. This also is to be expected; the acetic acid solution being less ionised than the HCl solution. It seems therefore to be necessary, if only one standard ferrocyanide solution is to be used, to standardise this solution with a weakly HCl acid solution, and when an acetic acid zinc solution is at hand to be titrated, either to make it ammoniacal and then weakly acid with HC1; or if the titration is carried on directly in the acetic acid solution to add a drop of HCl to the uranyl acetate drop on the spot-plate.

The standardisation of the potassium ferrocyanide solu tion in an acetic acid and ammonical zinc solution with the object of determining the factor for converting the value on zinc obtained in an acid solution to the value on zinc for titration in an ammoniacal solution was carried on as follows:

0'20-0'25 grm. of C.P. electrolytic zinc was dissolved in 10 cc. concentrated HCl, then 10 cc. H2O added, the solution boiled for a couple of minutes, removed from heat, 20 cc. NH,OH (1:1) added, 5 cc. concentrated HCI added, the solution again boiled for a couple of minutes, cooled, and diluted to 250 cc. at standard temperature. Of this solution 25 cc. portions were pipetted off into 250 cc. beakers. If the object was to titrate in an acetic acid solution the HCI acid zinc solution in the beaker was made ammoniacal to litmus then just acetic acid, 75 cc. water added, the solution heated to nearly boiling, and the titration carried on at 70-80° C., as described in No. 7), with the exception that a drop of HCI was an earlier article by the writer (Canadian Chem. Journ., added to 1 drop of the uranyl acetate (4 per cent) on the

spot-plate befor titrating.

K4Fe(CN)6. 3H2O (23735), the equation being :