200 On a pretended Formation of Oxalic Acid. 
certainly imitate every tint in nature ; with gamboge and carmine 
the prismatic red, and all the other gradations of orange, may be. 
made: and carmine with Antwerp blue gives the prismatic vio~ 
let, indigo, &c. But if instead of carmine he takes vermilion, 
or any other pigment of the hue of the prismatic red, he will find 
it impossible by joining it with blue to produce crimson, pink, 
violet, or any of the purples. 
On looking through the prism, or a convex lens, objects are 
tinged on their edges with a fringe of colour ; according to the 
relative positions of light or dark, that fringe is either yellow 
running into prismatic red, or blue running into violet. These 
two fringes united in the prismatic spectrum form the whole 
range of colours there shown. But, from what I have said, I think 
it is evident that it is deficient one third of the circle, which 
third includes the true primary colour of red with its most im- 
mediate compounds, 
1 am unpractised in writing ; but if I have advanced any thing 
that may be useful, in language that may be understood, I hope 
that any defect of style will be treated with indulgence. 
Tam, sir, yours respectfully, 
Tuomas HarGREAVES. 
P{S.—Is Mr.Sowerby’s work on Colours published ?* 
To the Editors of the Phil, Mag. 
XL. On the pretended Formation of Oxalic Acid in a Mixture 
of Alcohol and Sulphuric Acid. By M. VocErt. 
A CONSIDERABLE time has elapsed since M. Cadet de Gassi- 
court announced, that oxalic acid could be formed by the sim- 
ple contact of sulphuric acid and alcohol. The author expresses 
himseif in the following manner{ : “ I made a mixture of equal 
weights of well rectified aleohol and sulphuric acid : this mixture 
remained at rest for about thirty hours. At the end of this pe- 
riod I perceived at the bottom of the flask, and attached to the 
lower sides, a quantity of crystals about ten or twelve millimetres 
long, and formed by tetrahedral prisms terminated by a dihedral 
summit. After having decanted the liquor, [ examined these 
erystals ; and I ascertained, with the help of calcareous salts and 
reagents, that it was oxalic acid.’ M. Cadet then promises to 
resume this experiment ona large scale; which, so far as I know, 
he has not yet dove. 
This very remarkable result of the formation of oxalic acid by 
means of the sulphuric acid, has been nevertheless quoted in a 
* Yes; aud may be had of the ingenious Author, No. 2, Mead Place, 
Lambeth. 
~ + Annales de Chimie, tome Ixxxvi. p. 219. t Ibid. xxxv. p. 200. 
great 
