460 hitelligence and Miscellaneous Articles. 



The precipitate is to be diffused through cold water and mixed 

 with sulphuric acid to precipitate the barytes ; and it is better to 

 leave some digitalate of barytes undecomposed than to add too much 

 acid. By filtration a strongly acid, reddish-coloured solution is ob- 

 tained ; this is to be slowly distilled in a glass retort in order to se- 

 parate much of the water, and care is to be taken that the heat is 

 not too great. On cooling, a small quantity of a brown substance 

 decomposes, the clear liquor is to be poured off, and sufficient alcohol 

 is to be added to it to precipitate any digitalate of barytes which may 

 have escaped decomposition ; by evaporating the liquor in vacuo, 

 crystals are abundantly formed. 



In all these operations it is requisite to avoid the contact of air as 

 much as possible, for the digitalic acid is converted by it into a brown 

 substance : notwithstanding the evaporation in vacuo, the formation 

 of this substance cannot be prevented, and the crystals are conse- 

 quently formed in a liquid of a deep colour : the more the action of 

 the air is prevented, the purer are the crystals obtained. The ciy- 

 stals are to be separated by and pressed between filtering paper, dis- 

 solved in a small quantity of alcohol, and again crystallized in vacuo, 

 by which they are obtained white. 



The properties of digitalic acid thus obtained are, that it crystal- 

 lizes in long needleform crystals ; it possesses a slight peculiar odour, 

 which is increased by heat, and it yields a suffocating vapour, a small 

 quantity of which occasions coughing ; at a higher temperature it 

 melts, becomes black, and burns with a white flame ; it leaves a 

 charcoal which readily burns without residue ; no ammonia is pro- 

 duced during the decomposition by heat. 



The acid when pure is perfectly white ; but the action of light, 

 heat and air upon it is very great, readily converting it into a brown 

 product, which colours the solution, and from which it is difficult to 

 free it, and on this account the greatest care must be taken during 

 its preparation. "When the acid is dissolved in a small quantity of 

 water, it may be converted during evaporation by the water-bath 

 into a deep-coloured substance : this is itself acid, insoluble in water, 

 slightly soluble in aether, and readily so in alcohol. 



Digitalic acid becomes still more readily brown by the action of 

 alkaline bodies ; thus in preparing it excess of barytes must be 

 avoided. 



Digitalic acid has a sour but not disagreeable taste ; it immediately 

 reddens litmus paper, expels carbonic acid from carbonates, and 

 forms digitalates, and combines directly with basic oxides, and the 

 soluble salts which it forms become readily yellow in the air. — Journ. 

 de Pharm. et de Ch., Avril 1845. 



PREPARATION AND PROPERTIES OF CERTAIN DIGITALATES. 



M. Morin states the properties of the following digitalates : — 

 Digitalate of Soda. — Obtained by exactly saturating the acid with 

 carbonate of soda, and evaporating the solution under the air-pump 

 vacuum. It is white, and crystallizes very well, but by exposure to 



