TOOKEY ON THE SDPARA’L’ION OF L1V.-On the Separation of Tin from Antirnon?y and on the Analysis of Alloys containing Lead Tin Antimony and Copper. BY CHARLESTOOKEY, F.C.S. Of the Metallurgical Laboratory Royal School of Mines THEseparation of tin from antimony with a view to their direct quantitative estimation has hitherto been regarded as an analytical process involving considerable difficulty on account of the similarity which exists in the behaviour of the compounds of those metals with reagents. The method proposed by Gay Lussac consists in precipitating the tin and antimony together by means of a strip of zinc; the weight of the precipitated metals having been ascertained they itre then redissolved in nitro-hydrochloric acid and the antimony TIN FROM ANTIMONY ETC.463 scparated from the diluted solution by a strip of tin the amount of' this metal origirially associated with the antimony being estimated hy difference The more reccnt method by Rose provides for the direct estimation of each metal the separ at'ion being cfl'ccted l~yfusing the oxides with hydrate of soda aud cligcsting the antimonate and stannate of soda produced with dilutcd alcohol the insoluble antimonatc of soda heing afterwards washed on a filter with alcohol of increased strength as the opcrntion of washing a1)proaches completion. Having had occasion to examirie some alloys containing lead tin arid antimony with small quantities of copper and having failed to obtairi suficieiitly accurate rcsults in the separation of tin from antimony by eitlicr of the processes mentioned I made several attempts to efwt the objcct in view but without success when the rcactiori betwecri the sulpiiides of tin mid antimony and hydrochloric acid (gas) occurrctl to me as likely to afford a method fyce from ohjcction.IVlieri tersulpliide of antimony is cxposcd to the action of hydrochloric acid (gas) decomposition is effected at the ordinary tcmperature vith production of sulpliide of hydrogen and ter-chloride of antimony which xlieri gently heated is easily iwlatilized in a current of the gas. Protosulphide of tin Then treated in a simiIar manner is also clecomposed the products of decomposition being sulphide of Ii~drogc~i and proto-chloride of tin icliicli may be licatetl to incipient fusion in an atmosphere of Iiydrodiloiic acid without undergoing any further change.A iicccssary coliclit ion therefore to tlic success of a separation by iiieatis of tlic rcactions just stated \rould be that the tin should exist in solution in the state of protoside. By tlie method of analysis to be further dcscrilml tlie tiii was obt:tiiieill in the state of' hichloride and in endeavouring to efk'ect the reduction of the bichloride to tlic state of protocliloride an esprinient was made to ascertain the action of metallic iron upon the niised chlorides of tin and antimony in presence of an excess of hydrochloric acid the result of which mas that while tlie hichloride of tin was reduced to protochloride the wliolc of the antimony appeared to be separated in the metallic state.Gmelin states on the authority of Fischer that iron does not precipitate tin from tlie protochloride at the boiling heat. To see how nearly separation could be effected by iron in the presence of OM TOOKEY OX THE 8EPARBTJOX OF hydrochloric acid 6.03 grs. of pure antimony and 4.16 p.of tin were dissolved in hydrochloric acid with addition of a few drops of nitric acid; the solution was diluted with water and after adding more hydrochleiic acid digested at a gentle heat with 15 grs. of thin sheet iron until thc whole of the iron was dissolved ; a considerable quantity of cold water was then added and the antimony collected on a weighed filter after being washcd with water and dried the antimony weighed 6-02grs.In a second ex- periment '3.145grs. of pure antimony and 1.065 grs. of pure tin were dissolved as before; thc antimony in this case after drying weighed 9-18 grs. the tin was precipitated from the filtrate by aulphuretted hpdrogcn tha protosulpliide of tin dried and converted into binoxidc by careful ignition the amount of binoxide obtained was 1.36 grs. containing 1.069 grs. of metallic tin. In the analyses of the alloys containing lead tin and antimony with small quantities of copper the ordinary method for separating tin and antimony from other metals was used viz. oxidation with nitric acid the action being promoted by heat and the excess of acid expelled by evaporation the nitrates of lead and copper were removed by washing on a filter with hot water.By pro-ceeding in this manner it was found in two analyses of the same alloy that the amounts of lead and also the collective weights of the oxides of tin and antimony differed to a considerable extent. The same discrepancy was observed whether the acid used for oxidation was in the concentrated state or previously diluted with water. In order to ascertain the source of error the oxides of tin and antimony were examined and found to contain oxide of lead in a state of combination in which it could not be separated by washing with water and to aee whether the application of heat affected the result two equal weights (10 grs.) of the same alloy were taken one was treated in the usual manner heat being applied to promote the oxidation by nitric acid the excess of acid being expelled by evaporation; boiling water was then added and after perfect washing the mixed oxides weighed on ignition 8.92 gre.The other was oxidized by nitric acid withont the applica- tion of heat and the resulting oxides weighed 9-31grs. The application of heat causes therefore a large proportion of the lead to remain with the oxides of tin and antimony. When an alloy of lead and antimony is heated with nitric acid the TIN PBOM ANTIJIONY ETC. latter metal is converted into antimonic acid which combines with the oxide of lead the resulting compound being insoluble in water. That the whole of the lead might be separated from the other metals the following process was employed.The alloy was oxidized by nitric acid but little more acid being used than was necessary for oxidation; after removing the excess of acid by evaporation at a low temperature the residue was digested with hot water the oxides of tin and antimony being collected on a weighed filter and aftcr perfect washing dried at 110-120° C. After ceasing to lose weight,. they were carefully transferred to a glass boat; the filter with the small portion of oxides still adhering to it was again dried and weighed the difference between the two weights giving the amount of oxides operated upon. The boat was then placed in a condensing apparatus through whioh a slow current of hydrochloric acid was transmitted and wheu the contents of the boat had becomeliquid fiom the absorption of gas a gentle heat was applied in order to distil over the chlorides of tin and antimony.When the distillation was nearly finished a greater heat was used to expel the last tpces of hichloride of tin and the tube having cooled the boat was withdrawn and its contents (chloride of lead) dissolved out and added to the solution containing the nitrates of lead and copper. These two metals were determined as usual the solution being evaporated nearly to dryness with a slight excess of sulphuiic acid thc sulphate of lead washed with water acidified with sulphuric acid and the oxide of copper precipitated from the filtrate by a solution of potash. The chlorides of tin and antimony were poured into a small beaker ;the apparatus rinsed out with dilute hydrochloric acid and after adding more hydrochloric acid the solution was heated gently and digested with metallic iron (as pure as possible) until the whole of the iron had dissolvecl cold water was then added the antimony collected on a weighed filter and after mashing with cold water dried at 110" C.The filtrate from the antimony if not sufiiciently dilute was mixed with water and then saturated mith sulphuretted hydrogen. The salphide of tin being afterwards converted into binoxide by ignition. In order to simplify the process as much as possible the following plan was eventually adopted. Ten grains or more 466 TOOKEY ON THE SEPARATION OF TIN ETC. of the alloy to be analysed were introduced into a small piecc a of apparatus having the following form sufficient nitric acid to com-plete the oxididation was poured upon the alloy by means of a funnel-tube ; the end a was corked and the oxida- tion effected at a moderate tempera- ture.When the alloy had been con- verted into a perfectly white mass the excess of acid was expelled by attach- ing a tubc and cork to CL and causing a gentle current of air to traverse the apparatus either by meam of an as-b pirator or a pair of bellows; during this operation the apparatus should be heated sufficiently to cause the evaporation of the excess of nitric acid. The end a was tiow connected with an apparatus for genrrating dry hydrochloric acid (which should be made from fused chloride of sodium arid sulphuric acid) while the end b was immersed in a small quantity of water contained in a beaker ;the remaining part of the operation may be conducted as in the former process care being taken not to distil the volatile chlorides too rapidly and to avoid the fusion of the chloride of lead until all the bichloride of tin has been expelled.The iron employed to precipitate the antimony should be in the form of thin sheet about three times the weight of the antimony present being usually sufficient for complete precipitation. It is necessary that the flask for generating the hydrochloric acid be provided with a funnel-tube dipping just below the surface of the fluid in order to prevent the too rapid absorption of the gas by the water which is used to condense the chlorides of tin and antimony.