224 An ANALYSIS of 
For the fake of thofe who may have occafion to undertake 
fuch chemical enquiries as that defcribed in the above paper, I 
{hall here mention the method by which I colleéted and weighed 
the fmall quantities of fediments or precipitates, which I ob- 
tained in fome of thefe experiments. In moft cafes, the turbid 
liquor was left at reft in a cylindrical glafs, until the fediment 
was fo well collected at the bottom, that the greateft part of the 
liquor was quite clear, and then this clear part was carefully 
decanted ; the reft, which could not be decanted without di- 
fturbing the fediment, was fhaken, and poured gradually into 
a {mall filtre, that the fediment might be collected upon the 
filtre, and afterwards wafhed on it, by pafling diftilled water 
through it repeatedly. And this part of the procefs was much 
facilitated by the preparation of the filtre, and fome other little 
manceuvres. When, for example, I ufed for my filtre a piece 
of paper about four inches in diameter, I began by folding it, 
and giving it the proper form; then I fpread it open again, and - 
warming it, I applied melted tallow or bees wax to the margin 
of it all round, until it was foaked therewith to the breadth of © 
a full inch from the margin inwards, the middle part of it be- 
ing carefully preferved clean. As foon as this was done, and 
while it was yet a little warm, it was folded again into the pro- 
per form of a filtre, and retained in that ftate until it was cold. 
On a filtre prepared in this manner, it is much more eafy to 
collect a fediment together, and to wafh it clean, than on an or- 
dinary filtre. In the firft place, no part of the fediment ad- 
heres to or is depofited on that part of the paper which was 
foaked with tallow. The whole is collected on the clean part 
of the paper, and after it 1s collected there, I condenfe it into 
the centre as much as poffible, by dropping the diftilled water 
on the margin of that clean part all round, or a little above. 
that margin, by which pradtice the fcattered particles of the 
fediment are wafhed down into the bottom. Sometimes | ap- 
ply what may be called a capillary jet of the diftilled water, di- 
rected. 
