450 Memoir on Sulphuric Ether, 
erporisnpniatitt to. be led into a lebyrinth 9 
error. 
_ The bulk of the ether eat in sida stale 
has, I find, of late years been prepared by 
one manufacturing house in the neighbour- 
hood of London. Three qualities of. the 
article are made according to the different - 
uses intended. The highest quality is only 
made for particular purposes, and is therefore 
not very commonly met with; it is about .73 
specific gravity; the second quality is that 
intended for medicine; it is of .75 specific 
gravity, and is that with which all the coun- 
try druggists and apothecaries are or ought 
to be supplied as a standard uniform article ; 
3t is that which I have always met with in the 
shops, and which I have taken for genuine 
ether in my former experiments.—The third 
quality is of the specific gravity .78 or 379 
usually ; of course it is much inferior to. the 
last in purity. But it may be proper to. ob- 
serve, that this is the first state of the other 
two qualities; they being produced from 
this by ulterior processes called rectification. 
It is well known that sulphuric ether is pror 
cured by distilling, a mixture of sulphuric 
acid and. alcohol. The proportions usually 
prescribed are equal weights of concentrated 
