\\\ a glafs funnel. The precipitated earth will remain on the 

 filter; poiir on this a pound or more of hot water gradually^ 

 until it paifes taltelcfs : tatce up the filter, and let the earth 

 dry on it until they feparate eafily. Then put the earth into 

 u cup of Stafford (hire ware, place it on hot fand,, and dry th« 

 earth until it ceafes to (tick to glafs or iron; then pound It, 

 and reduce it to powder in the cup with a glafs peftle, aiid 

 keep it a quarter of an hour in a heat of from 470° to 500^. 



^* 4thly. The <,'arth being thus dried, throw it into a Flo- 

 rence flalk, and weigh it; then put about one ounce of fpirit 

 of fait into anoth<^r llalk, and place this in the fame fcale as the 

 earth, and counterbalance both in the oppofite fctde: this 

 being done, pour the fpirit of fait gradually into the {ia(k that 

 contains tljc earth ; and when all etfervefccncc is over (if there 

 be any) blow into the iialk, and obfcrve what weight mull be 

 added to the fcale containing the flafks to reftore the cqiiili- 

 "hiiuni; fubtracl this weight from that of the earth, the re- 

 mainder is a weight exa6lly froporthued to the weight of mere 

 alkali ofthat particular fpecies which is contained in one ounce 

 of the fubihnce examined ; all befidc is fupcrfluous-matter. 



" I have faid that alkalies of the y^zw^ yJ^t-T/V^ may thus 

 be direiS^ly compared, becaufe alkalies of different fpecies can- 

 not but require the intervention of another proportion; and 

 the reafon is, becaufe ^^r/^z/ quai.t'ties of alkalies of diiferent 

 fpecies precipitate unequal quantities of earth of alum. 'J'hu« 

 100 parts, by weight, of mere vcgcUihU alkali precipitate 78 

 of earth of alum; but too parts of wmrrt/ alkali precipitate 

 170,8 parts of that earth. Therefore the precipitation of 78 

 parts of earth of alum by vegetable alkali denotes as much of 

 this as the precipitation f)f 170,8 of that earth by the mineral 

 .alkali denotes of the mineral alkali. Hence the quantities of 

 alkali in all the different fpecies of pot-aihes, pearl-a/lies, wec^ 

 or wood*afhes, may be immediately compared by the above 

 teli:, as they all contain the vegetable alkali ; and the different 

 kind of kelp or kelps manufa<Slured in ditlcrcn't places, an4 

 the diOercnt forts of barilla, may thus be compared, becaufe 

 they all contain the mineral alkali. But kelps and pot-aflie?, 

 as they contain different forts of alkali, can only be compar<i-d 

 together by means of the proportion above indicated." 



[Tg be contiiiu.ed.] 



XXXIV. 



