1 10 Dr. Prout on simple Alimentary Substances. 



Tartaric Acid in crystals is composed of 



Carbon 32*0 



Water 36*0 



Oxygen .... 32*0 

 a composition assigned to it by Dr. Thomson in his work just 

 quoted. 



Malic Acid. — I am not acquainted with any analysis of malic 

 acid except that of M. Vauquelin*, which has not, I believe, 

 obtained much confidence among chemists, chiefly on account 

 of the large proportion of hydrogen which he assigns to it. 

 The acid I employed was obtained from the berries of the 

 mountain ash by a process very similar to that of Mr. Dono- 

 van. It was not analysed per se, but in combination with 

 lead, with lime, and with copper, and was found, abstracting 

 water not essential to its composition, to consist of 



Carbon 40*68 



Water 45*76 



Oxygen 13*56 



This acid, in many points of view, may be regarded as one 

 of the most interesting and important of all the vegetable 

 acids. 



Saclactic Acid. — The unexpected composition of this acid in- 

 duced me to investigate its properties more fully than I had 

 otherwise intended. What I first employed was obtained 

 from the sugar of milk, and hence was tolerably pure, though 

 not perhaps completely so. Latterly, I have preferred that 

 prepared from gum, which, though exceedingly impure as 

 first obtained, may be easily and completely purified by the 

 following simple process. 



Add ammonia in slight excess to the impure acid, and af- 

 terwards as much boiling distilled water as will dissolve the 

 saclactate formed. Filter the solution while boiling hot, and 

 then evaporate it very slowly nearly to dryness. The saclac- 

 tate of ammonia will be separated in the form of crystals, 

 which are to be washed with cold distilled water till they be- 

 come quite white and pure. They are now to be again dis- 

 solved in distilled water, and the boiling saturated solution 

 permitted to drop from a filter into cold diluted nitric acid. 

 This latter of course decomposes the saclactate, and precipi- 

 tates the saclactic acid in a state of perfect purity. Thus ob- 

 tained, this acid was found to consist of 

 Carbon . . . . 33*33 



Water 44*44 



Oxygen .... 22*22 



* Ann. de Chimie et de Physique, torn. vi. 337. 



results 



