Intelligence and Miscellaneous Articles. 457 



considered as a true acid, and as incapable of combining with acids 

 as a base to form salts. 



The following are the reasons given by the author for adopting 

 these opinions : — The action of peroxide of tin as an acid upon he- 

 matin, and on examining the compound which it forms with acids, no 

 one of them possesses the properties of a salt ; nitric acid dissolves 

 but an inappreciable quantity ; it combines with sulphuric acid, but 

 the compound is decomposed by a few seconds' ebullition into sul- 

 phuric and stannic acids ; and the same happens with the most di- 

 stinctly marked metallic acids, as with antimonic acid : as to the 

 compound of stannic with hydrochloric acid, may it not be compared 

 to the chlorides of arsenic, sulphur, phosphorus and antimony, which 

 have never been considered as true salts ? Lastly, stannic acid does 

 not combine with organic acids, or at any rate they form very un- 

 stable compounds, which are totally decomposed by water ; under 

 these circumstances M. Fremy is of opinion, that stannic acid com- 

 bines with other acids to form double acids of little stability, like 

 other compounds of this nature, instead of salts. Compounds of 

 acids frequently occur in chemistry, and the complete decomposition 

 of them which water effects is to a certain extent characteristic of 

 them. 



M. Fremy states an experiment, which in his opinion demonstrates 

 positively that peroxide of tin is always an acid, even when separated 

 from combination with hydrochloric acid : — if a solution of bichloride 

 of tin be decomposed by carbonate of potash or soda, a precipitate is 

 obtained, which is not peroxide of tin, but stannate of potash or of 

 soda, which are insoluble in water containing a salt of potash ; if, 

 on the other hand, the bichloride of tin be treated with an insoluble 

 carbonate, as that of lime or barytes, the stannic acid is then preci- 

 pitated, possessing all the properties of an acid. — Ann. de Ch. et de 

 Phys., Decembre 1844. 



METASTANNIC ACID. 



M. Fremy observes, that the experiments of Berzelius and his own 

 show that there are two modifications of stannic acid which possess 

 properties entirely different. One of these is prepared by precipita- 

 ting bichloride of tin, as already stated, by an alkali or by carbonate 

 of lime or barytes ; and to this M. Fremy proposes to restrict the 

 name of stannic acid, whilst for the acid prepared by acting upon the 

 metal with nitric acid, he proposes the name of metastannic acid. 



This is always formed as a hydrate, and M. Fremy found, that 

 after drying it by a current of air at the usual temperature, taking 

 the mean of three experiments, it contained 19"8 per cent, of 

 water. Now, taking 58 as the equivalent of tin, and 74 as that of 

 the binoxide, it is evident that a compound of one equivalent of the 

 metastannic acid and two of water must contain 19*5 per cent, of 

 water. 



When hydrated metastannic acid is exposed to a temperature of 

 284° Fahr., or to a vacuum, it loses very nearly 8 per cent, of water ; 

 if it parted with one equivalent, it would, of course, amount to 9'7. 



