[29 J 
of allum; an hepatic fmell was perceived during the precipitation 
of the allum, and the earth was of a dirty colour. 
I rrrep alfo another fort of afhes which I had from a chandler ; 
it was of a whiter colour and cleaner. The folution of an ounce 
of it in fix ounces of water precipitated only 5,5 grains of earth 
of allum, and therefore contained but 8 grains of mere alkali. 
Tuere is a remarkable circumftance attending thefe afhes, 
namely, that if they be much calcined they feem to lofe their 
alkaline properties, and the folution no longer precipitates that 
of fublimate corrofive reddifh, as alkalies not thoroughly aerated 
do. What this circumftance depends on I have not as yet 
examined, but am almoft certain it proceeds from the prefence 
of common falt, as fixed alkalies and common falt melt very eafily, 
and thus unite to the earths. 
To eftimate the goodnefs of different afhes, fome have recom- 
mended the ufe of an hydrometer, whereby to difcover the 
{trength of folutions of equal weights of thefe afhes in equal 
quantities of water; but as this inftrument is equally affected 
by the prefence of neutral falts, as of alkali, it becomes ufelefs. 
Table 
