Intelligence and Miscellaneous Articles, 459 



3H0, in which case its composition in 100 parts would be, acid 75* 1 , 

 potash 15, water 9*9 ; this is, of course, a neutral salt, containing 

 one equivalent each of acid and base. 



In order to be still more certain as to the equivalent of metastannic 

 acid, the author formed some acidulous metastannates, by dissolving 

 the neutral metastannate above described in a large quantity of water 

 and precipitating the solution by alcohol ; the salt thus obtained is 

 gelatinous, soluble in water, and has a strong alkaline reaction. It 

 often becomes insoluble by drying, even at the temperature of the 

 air. This salt yielded by analysis, — 



Metastannic acid. . . . 82*6 

 Potash 8-7 



Representing this salt by 2Sn', KO, 5H0, it would consist of acid 

 82*9, potash 8" 7, water 8*4 in 100, or it is a bimetastannate ; a cor- 

 responding soda salt was formed by the same means. 



The author observes, that there exist but few examples in che- 

 mistry of salts undergoing decomposition by heat, when one of the 

 elements composing them undergoes no change of state ; but the 

 salts now described when heated are decomposed and become in- 

 soluble, the acid separating from the base and water being disengaged 

 during the calcination ; when the calcined salt is treated with water, 

 the alkali is dissolved, and the metastannic acid remaining insoluble 

 contains mere traces of the base. The production of hydrate of 

 potash when metastannate of potash is heated, prevents the direct 

 determination of the quantity of water contained in this salt. — Ann. 

 de Ch. et de Phys., Decembre 1844. 



ON DIGITALIC ACID. BY M. PYIIAME MOKIN. 



To prepare this acid, the leaves of the plant are to be treated with 

 hot water ; the infusion is acid, and is to be evaporated by the water- 

 bath to the consistence of a thick syrup ; to the residue a large quan- 

 tity of alcohol is to be added until it produces no further precipita- 

 tion ; it is to be suffered to remain for some days till a deposit is 

 formed, and which ought not to be bitter, but which is so if the 

 alcohol was too strong. 



The liquid is then to be filtered, and distilled in a water-bath till 

 it becomes a thick extract, which is to be treated with pure sulphuric 

 aether, and kept at a moderate heat for an hour and eventually boiled ; 

 this operation is to be repeated several times. 



The sethereal tinctures thus obtained are acid, and have a slightly 

 greenish-yellow colour, especially the first portions. By this pro- 

 cess the bitter principle, or digitalia, and the digitalic acid are dis- 

 solved ; to this sethereal solution barytes in fragments is to be gra- 

 dually added, which forms a yellowish precipitate, and when any 

 remains insoluble, or the solution restores the blue colour of red- 

 dened litmus, enough barytes has been added. 



The liquor, which contains only digitalia, but not perfectly pure, is 

 then to be filtered. The precipitate is to be collected, which is to 

 be washed with sether to remove all the bitterness, and then with 

 alcohol, till it passes but slightly or not at all coloured. 



