Manchester Memoirs, Vol. lix. (191 5), No. \%. 57 



The formula for albumen in the Note-book is different 

 from that of gelatine by possessing one atom of carbon 

 more. The date in the Note-book is October, 181 1. 



Sheet 24. 



Plate VII. 

 The formulae for four organic acids, inscribed " oxalic," 

 ' 'citric," " acetic," " tartaric." Oxalic acid is represented 

 as C 2 3 , a compound of CO and CO.,. Acetic acid is 

 CHO, and citric and tartaric acids are represented as 

 each having a central atom of oxygen, surrounded in the 

 case of citric acid with three of these CHO groups 

 symmetrically placed ; in the case of tartaric acid with 

 four of these CHO groups. In 181 1 Dalton had the idea 

 of an important part played by the CHO group, which 

 he called the " vegetable atom " (Note-book iv., 56), with a 

 weight 13*4. This idea might have been fruitful at the 

 time : with modern atomic weights the grouping would 

 have become CHX), which, as formaldehyde, seems to 

 play a most important part in natural organic syntheses. 

 Dalton published very little of his organic chemical work, 

 however ; indeed, it extended only occasionally beyond 

 analyses of a few organic acids and their salts. 



An exact reproduction of the formulae for citric and 

 tartaric acids has been found once only, in a note-book 

 entitled, "Salts, Oxides, Sulphurets," which contains a 

 laborious compilation of the composition by weight and 

 the atomic composition of many of the compounds of 

 metals. This note-book received additions during many 

 years, and was probably intended to form a basis of 

 volume II. of the " New System," not only the published 

 part but also another projected part dealing with the salts 

 of the metals. The formulae of citric acid and tartaric 

 acid in the note-book and on the sheet probably belong 



