458 Intelligence and Miscellaneous Articles, 



When hydrated metastannic acid is dissolved in potash or soda, a 

 salt is obtained, which, when decomposed by an acid, precipitates 

 gelatinous metastannic acid, possessing the same characters as the 

 acid before solution ; it combines, for example, with hydrochloric 

 acid, and forms a compound perfectly similar to that obtained by 

 treating hydrated metastannic acid with hydrochloric acid. 



Metastannic acid, however, which has been precipitated from pot- 

 ash or soda, differs from the acid which has not been dissolved in an 

 alkali in a very important property, which is that of becoming so- 

 luble in ammonia in all proportions, whereas the acid before solution 

 in the alkali is entirely insoluble in this alkali : these two modifica- 

 tions of metastannic acid evidently differ by a proportion of water ; 

 for when the metastannic acid which is soluble in ammonia is dried, 

 even at a very gentle heat, it becomes totally insoluble ; if also it be 

 boiled for some time in water, it loses its solubility in ammonia : it 

 was found impossible to determine the quantity of water retained by 

 this acid, for the means required to get rid of the hygrometric water 

 would have destroyed its solubility in ammonia ; these acids, how- 

 ever, form similar salts with bases. 



When metastannic acid is heated in concentrated sulphuric acid, 

 a large quantity is dissolved, and a compound is formed which is very 

 soluble in alcohol and in water ; the aqueous solution is decomposed 

 by boiling, and precipitates metastannic acid ; this acid contains 

 19*6 per cent, of water; it is insoluble in ammonia. 



The author concludes, both from the quantity of water and of bases 

 with which metastannic acid combines, that it is composed of 3 equi- 

 valents of tin and 6 equivalents of oxygen, Sn^ O*" ; in this case its 

 number, hydrogen = 1, will be (tin 174 + oxygen 48) = 222. 



FORMATION AND COMPOSITION OF CERTAIN METASTANNATES. 



M. Fremy states that the metastannates of ammonia, potash and 

 soda are soluble in water, whereas the other metastannates are inso- 

 luble therein ; the alkaline metastannates are obtained by the direct 

 solution of the acid in the bases ; the others are prepared by double 

 decomposition. The soluble metastannates do not crystallize, and 

 are precipitated by alcohol ; great difficulty was experienced by the 

 author in obtaining these compounds of uniform composition, so as 

 to determine their equivalent. 



Metastannate of Potash. — To prepare this salt by dissolving the 

 acid in the alkali, the solution was treated with alcohol, and a gummy 

 deliquescent precipitate was obtained, which, after washing with al- 

 cohol, was quickly dried between folds of filtering paper, and imme- 

 diately transferred to a vacuum. 



This salt consisted of, — 



Metastannic acid. ... 75*8 



Potash 14-1 



Water IQ-l 



100- 



The author considers this salt to be represented by Sn' 0^, KO, 



