[ntclKgence and Miscellaneous Articles. 477 



water dissolving it which effected the decomposition, Lowenthal 

 made the following experiments. 



A gramme of anhydrous perchloride of tin Avas treated in two ex- 

 periments with 100 and 60 cubic cent, of cold water. The one 

 solution began to lose its clearness after 2 or 3 hours, the latter not 

 till after 36 hours, then very feebly, and it was not milky until after 

 a week. Having thus ascertained the proportion of water which 

 might be employed without fearing decomposition, he mixed, — 



a. 0"5 grm. perchloride with a solution of 1 grra. crystallized 

 sulphate of soda in 30 cub. cent, water at 64° F. A precipitate 

 was immediately formed. 



h. The experiment a. was altered byadding 0"125 grm. hydrochloric 

 acid, l'r2 sp. gr., to the perchloride of tin. The liquid was at first 

 turbid, and after one minute the decomposition was complete. 



c. On using 0'25 grra. hydrochloric acid, it was not complete until 

 after 3 minutes, with 0"375 grm. 10 min., with 0"5 grm. 43 min., and 

 with 0'75 grm. of acid the liquid remained clear for several hours. 



d. 0'5 grm. perchloride with 0"5 grm. hydrochloric acid and 30 cub. 

 cent, water containing 2'5 grms. crystallized sulphate of soda, were 

 mixed at 64° F. : remained at first clear, and the decomposition was 

 not completed until after 7 minutes. 



c. The experiment c. with 0'5 grm. acid repeated. The liquid 

 at first clear, immediately gave a precipitate when heated to about 

 108° F. 



f. 0*5 grm. protochloride treated with only 15 grms. water con- 

 taining 1 grm. sulphate of soda. Liquid at first clear, gave a precipi- 

 tate when heated which did not disappear on cooling. 



g. Metastannic acid long digested with hydrochloric acid and the 

 residue dissolved in water. On the addition of sulphate of soda the 

 decomposition ensued immediately. It follows from these data that, — 



1 . The decomposition takes place in the cold only when a certain 

 quantity of water is present. 



2. In the absence of free acid, with an adequate quantity of water 

 and with about 2 equivs. sulphate of soda to 1 equiv. perchloride of 

 tin, the decomposition takes place immediately. 



3. Free acid hinders the decomposition more or less in proportion 

 to its quantity. Its influence may be removed by the careful addition 

 of ammonia. Cliloride of ammonium does not cause the decompo- 

 sition of the perchloride. 



4. With equal quantities of free acid the decomposition takes 

 place more rapidly, the greater the quantity of sulphate of soda. 



.O. Heat favours the decomposition in all cases. 



Lowenthal likewise found that the sulphates of magnesia, alumina, 

 protoxide of manganese, iron, zinc and cojiper, peroxide of iron, pro- 

 duced the same decomj)osition; moreover, nitrates of soda, ammonia, 

 baryta, zinc and copper. 



He found that the j)recipitate was pure hydrated oxide of tin, and 

 never contained any of the acid of the precipitant. He considers the 

 decomposition to be represented by 



SnCl^ + 4NaO,S03 + 4HO = SnO^ 2H0 (?) + 2NuCl 

 + 2(NaO, HO, 2S03). 



