4S REPORT — 1875. 



Quantity of leather tanned in Bristol sufficient to provide soles for nine million 

 pairs of boots annually. Various articles have been used as substitutes for leather, 

 but very few have stood the test of time. 



Great importance of preventing the tannic tui-ninr/ into r/aUic acid. — Unfortunately 

 the trade generally are ignorant on chemical subjects^ and will receive with much 

 pleasure any information on the subject. 



On the Separation of Lead, Silver, and Mercury, with a proposed process for 

 estimation of Lead. By T. Fairley, F.U.S.E. 



These metals form a group generally precipitated together as chlorides, and 

 various processes, more or less perfect, have been devised for their separation. Thus 

 the silver chloidde may be separated by ammonia, or the lead chloride by boiling 

 with much water,_ or the niercurous cliloride by boiling with nitric acid or aqua 

 regia. This last is tedious and is open to the objection mentioned by Fresenius, 

 that mercuric chloride volatilizes with the vapour from boiling water. 



In the study of the reactions of hypochlorites and while engaged in teaching the 

 ordinary course of analysis, the author ascertained that the conversion of mercurous 

 chloride into soluble mercuric chloride is instantaneously effected by boiling with 

 alkaline hypochlorite, taking care that tlie solution remains acid throughout. 



The hypochlorite used may be potassium, sodium, or calcium hypochlorite. The 

 author finds the most convenient to be a solution prepared by passing chlorine into 

 a lO-per-cent. solution of sodium hydrate until the impurities (alumina &c.) con- 

 tained in it begin to separate out. On then adding a small proportion of the sodium 

 hydrate solution, say about one tenth of the quantity saturated with chlorine, we 

 obtain a liquid of convenient strength, and which when kept in the dark remains 

 almost unchanged. 



Of course in the absence of acids &c. affecting the solubility of calcium compoimds, 

 solution of ordinary bleaching-powder may be used. 



^ The separation of lead from mercurous salts may be readily performed by a con- 

 tinuation of the above process. If any free acid be present, add sodium acetate or 

 hydrate and sufficient acetic acid to ensure an excess of the latter throughout the 

 process. On boihnij with hypochlorite all the lead is precipitated as brown dioxide. 

 The dioxide so obtained is pure ; and as no lead remains in solution the author has 

 confidence that this may prove an accurate process for the estimation of lead. 



On a netv Method of prepariny Periodates, ivith Apiplication as a Test 

 for Iodine and Sodium. By T. Faiklet, F.R.S.E. 



When we boil any iodide or iodate with excess of alkaline hydrate and hypo- 

 chorite, then, if sodium salts be present, a crystalline precipitate is after some time 

 thrown down consisting of sodium periodate. 



Using potassium hydrate and hypochlorite this test may be used to ascertain the 

 •presence of sodium compounds in any substance added to the boiling liqiud. In a 

 solution of about .30 cub. centims. in volume less than 0-1 gramme can readily be 

 detected ; and with a smaller V9lume more minute quantities nniy be detected. 



As a test for iodine it is of course unable to take the place of more delicate well- 

 known tests ; but it is useful as affording in any case confirmatory evidence. 



On neiv Solvents for Gold, Silver, Platimim, S,-c., ivith an Explanation of the 

 so-called Catah/tic Action of these Metals and their Salts on Hydror/cn 

 Dionide. By T. Faiexey, F.E.S.E. 



On the Use of Potassium Bichromate in Grove's and Bunsen's Batteries to 

 ensure constancy. By T. Faiuley, F.E.S.E. 



