H4 Humphry Davy's experiments and observations 
when the salt fused there was a slight scintillation, a little 
moisture appeared, and the gas given off received into lime 
water occasioned a very evident precipitation. 
It appeared from these experiments, that the colouring 
matter was a compound of either vegetable or animal origin. 
I threw some of it upon a hot iron, it emitted scarcely any 
smoke, and gave a smell which had some resemblance to that 
of prussic acid, but which was extremely faint. 
When hydrate of potassa was fused in contact with it, the 
vapours that rose had no distinct ammoniacal smell ; they gave 
indeed slight fumes to paper moistened with muriatic acid, 
but this is far from being an unequivocal proof of animal 
matter. I compared this colour with vegetable lake from 
madder, and animal lake from cochineal diluted to the same 
degree as nearly as could be judged, and fixed upon clays. 
The lake of madder, after being dissolved in strong muriatic 
acid, had its colour restored by alkalies, which was not the 
case with the ancient lake. The lake of madder likewise gave 
a much deeper tint to muriatic acid, and produced a tawny hue 
when its weak muriatic solution was acted on by muriate of 
iron ; whereas the ancient lake did not change in colour. 
The ancient lake agreed with the lake of cochineal in being 
rendered of a deeper hue by weak alkalies, and of a brighter 
hue by weak acids ; but it differed from it in being much more 
easily destroyed by strong acids. It agreed with both the 
vegetable and animal lakes in being immediately destroyed 
by a solution of chlorine. 
The lake made from cochineal produced much denser fumes 
when exposed to fused potash, and afforded a distinct ammo- 
niacal smell. The two modern lakes when burnt in oxygene 
