CHEMISTRY. 



M 





of deterioration varies with the purity, and, 

 above all, with the concentration of the acid 

 produced in the alembics. The presence of 

 nitrous compounds in the acid considerably 

 moments its action on the platinum ; and, by 

 increasing the strength of the acid, a greater 

 amount of platinum dissolves, becoming ten 

 tii i u -s greater than when concentrating 94 per 

 cent, or monohydrated acid. 



The question arises whether the observed 

 dot r duration is due to a simple mechanical 

 action, or whether the platinum is really dis- 

 solved. 



The following experiences reply to the ques- 

 tion : 



The presence of the lower acid compounds of 

 nitrogen in the liquids, coming from the lead cham- 

 ber*, greatly increases the dissolution of the plati- 

 num. 



An alembic, which had been in use for two years 

 in the chemical works at Thann, lost 12.295 kilo- 

 grammes in concentrating 4,309,000 kilogrammes of 

 06 B. acid of ordinary concentration that is to 

 say, of monohydrated acid, from 93 to 94 per cent. 



There has then disappeared, during this operation, 

 2.859 grammes of platinum to each 1,00) kilogrammes 

 of acid. 



The acid introduced into the alembic was con- 

 taminated with nitrous oxides. 



In order to destroy these compounds, M. Scheurer- 

 Kestner employed sulphate of ammonia for purify- 

 in? the acid. 



The dissolution of the platinum immediately do- 

 creased, and the next year the amount dissolved was 

 2.490 kilogrammes fora production of 1,843,000 kilo- 

 grammes of acid, being 1.220 grammes of platinum 

 for 1,000 kilogrammes of acid. 



During the following years the acid used in the 

 alembic contained sulphurous acid. It was free from 

 nitrous compounds. 



The dissolution of platinum fell to 0.925 gramme 

 to the 1,000 kilogrammes of concentrated acid, for 

 a total production of 17,516,000 kilogrammes of acid. 

 The loss in weight of platinum boikr had been but 

 16.178 kilogrammes. 



It does not appear that the small amount of chlpr- 

 hydric acid in the acids from the chambers, which 

 remained constant, influenced in a sensible manner 

 the solution of the platinum, whatever may have 

 been the degree of impurity of the nitrate of soda or 

 of the nitric acid usea for the preparation of the sul- 

 phuric acid. But, when the degree of concentration 

 exceeded 94 per cent. i. e., ordinary commercial 

 acid a much greater action was produced by the 

 acid on the platinum. 



As we have seen, the preparation of 94 per cent, 

 acid carried away from the distilling vessel a quan- 

 tity of platinum equal to near 1 gramme per 1,000 

 kilogrammes of acid. 



When the concentration is increased in order to 

 obtain 97 to 98 per cent, monohydrated acid, more 

 than 6 grammes of platinum is dissolved to the 

 1,000 kilogrammes of acid. 



In a platinum alembic, whose boiler weighed, when 

 new. 30 kilogrammes, in which was evaporated 

 180,000 kilogrammes of acid, brought to 97 to 98 

 per cent., the loss of weight of the metal was 6.070 

 grammes per 1,000 kilogrammes of acid. 



When acid holding 99i to 991 per cent, of monohy- 

 drated acid waa prepared, the platinum dissolved 

 readied from 8 to 9 grammes per 1,000 kilogrammes 

 of acid ; for a production or 102,000 kilogrammes 

 of acid of 994 per cent., the boiler lost 861 grammes 

 of platinum, being 8.444 grammes per 1,000 kilo- 

 grammes. 



This quantity of metal being large enough to make 

 it possible to recover by quantitative analysis, tho 



author endeavored to corroborate the above figure* 

 by weighing thu platinum obtained from certain 

 quantity of sulphuric acid of UHi per cent. ; 78.600 

 kilogrammes of this acid wan diluted with water, 

 current of sulphureted hydrogen gas parsed through 

 the solution, the precipitated sulphides, containing 

 lead and platinum, were dissolved in aqva-rtyin, tic 

 lead was all removed by precipitating it twice with 

 sulphuric acid, the solution having the charaeti ri-- 

 tic color of the salts of platinum as well as their 

 properties. 



Tho platinum was finally precipitated in the state 

 of sulphide and weighed after calcination. There 

 was obtained 0.617 grammes of metallic platinum, 

 being 8.380 grammes per 1,000 kilogrammes of acid, 

 u number which accords completely with the results 

 obtained from the industrial observations. 



Thymol a an Anti-Ferment. Thymol, ob- 

 tained by distillation from oil of thyme, occurs 

 in white, highly-aromatic crystals ; when dis- 

 solved in hot water in the proportion of 1 

 part per 1,000 it forms a fully-saturated solu- 

 tion possessing a neutral reaction. More con- 

 centrated watery solutions cannot be obtained, 

 for, when dissolved in greater proportions 

 than 1 in 1,000, the thymol evaporates. 

 From experiments made by L. Lewin it ap- 

 pears that 0.1 per cent, of this solution is suf- 

 ficient to prevent fermentation in sugary liq- 

 uids, no matter what the proportion of sugar 

 and yeast. Milk, to which a small quantity 

 of the thymol solution was added, did not be- 

 gin to show signs of coagulation till twenty 

 days later than milk with which an equal quan- 

 tity of water had been mixed. Filtered white 

 of egg in contact with the air was found to 

 grow putrid in three or four days, whereas 

 white of egg with which thymol-water had 

 been mixed gave not the slightest indication 

 of putridity after eleven weeks. The same 

 results were obtained in treating pus with 

 water and thymol : pus so treated at once lost 

 its putrid odor, and continued to be odorless 

 for five weeks, or until it had become dry. 



Estimation oftJie Strength of Astringent*, 

 It has been observed by F. Jean that astrin- 

 gents mixed with an alkaline carbonate absorb 

 a solution of iodine with a readiness like that 

 of the arsenite of soda. This absorption is 

 found to be directly proportioned to the quan- 

 tity of astringent matter present, 1 part of 

 dry tannic acid taking up 4 parts of iodine. 

 The solution of iodine required for the titration 

 of tannin is obtained by dissolving 4 grammes 

 of iodine in iodide of potassium, and making 

 up the solution to 1,000 c.c. with distilled 

 water. To standardize thi? solution, place in 

 a precipitating glass 10 c.c. of a solution of 

 tannin containing 0.1 gramme per cent., add 2 

 c.c. of an alkaline solution containing 25 per 

 cent, of crystalline carbonate of soda, and then 

 with a graduated burette drop tho solution of 

 iodine into this mixed liquid till a drop of the 

 mixture, taken up with the stirring-rod, ant? 

 placed upon a leaf of (torch-paper, produces a 

 very slight violet spot, which indicates the 

 presence of free iodine and the end of the op- 

 eration. The value thus obtained must be cor- 

 rected, that is to say, from the number of c.c. of 



