332 QUARTERLY JOURNAL. 



from oxalic acid fresh portions of oxygen, we have tartaric on 

 malic acid. Tartaric acid is formed by the elimination of 9 equi^ 

 valents of oxygen : the separation of 12 equivalents of the samej 

 element gives rise to malic acid. 



Hydrated oxalic acid C'*H*0'*^ — 0*=3 eq. of tartaric acid. 

 » " " C«^H«0"—0"=3eq. of malic acid. 



It is by a simple separation of water from the elements of malic 

 acid that citric acid is formed ; we know, that by the sole influence 

 of heat, we can produce, with citric acid, aconific acid, and with 

 malic acid lichenic and maleic acids. 



Malic acid C'«H«0'=^— Aq=:C'2H^O"=3 eq. of citric acid. 

 » C''H«0'=*— 3 Aq=C»=^H^O» =3 eq. of lichenic acid 



We may now consider the tartaric and malic acids as combina 

 tions of oxalic acid with sugar, gum, ligneous fibre, or their ele 

 ments. 



Tartaric acid. Oxalic acid. Dry grape sugar. 



So that, consequently, by the addition of new quantities of hydrc 

 gen, all these acids may contribute to the formation of suga: 

 starch and gum. In this metamorphosis, the alkalies, which wei 

 combined with the acids, should, as is self-evident, be set at libert) 

 they should recover the faculty of again performing the same part 

 It may, therefore, be believed that one equivalent of alkali ma 

 serve for converting 10, 20, and even 100 equivalents of carbc 

 into a principle of the plant. It is by time alone that the quantil 

 of the base present produces any difference. 



If a living evergreen plant assimilates, throughout the year, wi 

 the assistance of a given quantity of potassa, a certain quantity 

 carbon under any form whatever, a summer plant requires near 

 four times as much potassa to assimilate the same quantity in on 

 fourth the time. 



Gay Lussac fiirst observed that oxalic, tartaric, and citric acid 

 and sugar, ligneous fibres, &c., are brought to the state of carbon 

 acid by the contact of an alkali, at a high temperature. 



This course of decomposition is precisely the inverse of th 

 which occurs in plants. In the latter, the elements of water a 

 added to the combination of carbon to the carbonic acid, oxali 

 and tartaric acids, &c., are formed, owing to a separation of oxyge 



In the chemical operation indicated, the elements of water 

 presence are added to those of the oxalic and tartaric acids, &c 

 they are brought to the state of carbonic acid by a separation 

 hydrogen. 



Without disengagement of any gas, from the fact of the presen 

 of an alkali, the tartaric and citric acids are already divided^ at 





