Dr. Thomson on Oxalic Acid. 
95 
obtain a much greater quantity of oxalic acid from sugar than 
we can at present ; but nitric acid acts by removing one-half 
of the carbon in the form of carbonic acid ; the sugar deprived 
of this, resolves itself into oxalic acid and water. Suppose two 
particles of sugar acted on at once, the symbol for them will 
be 10 w + 6c + 8 h. Let three atoms of the carbon be 
removed by the action of the nitric acid, there will remain 
10 w -j- 3 c -f- 8 h. Now 
A particle of oxalic acid = 4, w -}- gc -f- 2/1 
Six particles of water = 6 zv - - -J - 6 h 
10 w gc 8 h 
which is just the quantity of oxalic acid left. This will give 
us some idea of the way in which the formation of oxalic acid 
by nitric acid is accomplished. And although the series of 
changes is probably more complicated, yet they are ultimately 
equivalent to the preceding statement. I allude to the for- 
mation of malic acid, which is said to precede the oxalic acid, 
and afterwards to be converted into it by the subsequent action 
of nitric acid ; but on the composition and formation of this 
latter acid, I avoid making any observations at present, as I 
propose to make them the subject of a separate dissertation. 
