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 

 mall here mention the method by which I collected and weighed 

 the fmall quantities of fediments or precipitates, which I ob- 

 tained in fome of thefe experiments. In mod 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 fmall filtre, that the fediment might be collected upon the 

 fUtre, and afterwards warned 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 

 manoeuvres. 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 depolited 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 is collected there, I condenfe it into 

 the centre as much as porTible, by dropping the diftilled water 

 on the margin of that clean part all round, or a little above 

 that margin, by which practice the fcattered particles of the 

 fediment are wafhed down into the bottom. Sometimes I ap- 

 ply what may be called a capillary jet of the diftilled water, di- 

 rected 



