I. -In'iheufual method of procuring pliofpliorus from tone- Eftimate of 

 duft, and fulphuric acid, the value of the ingredients is very ta'imnrphofpho- 

 fmall, the labour of the procefs, with the fuel employed for ms from bones. 

 the evaporation and diftillation form the principal confideration *^""^t 3s. per oz. 

 in eftimating the value of the product. 



One pound of bones calcined and pulverized with half a 

 pound of fulphuric acid, will produce, according to Fourcroy, 

 about three quarters of an ounce of piiofphorus; if the labour 

 and fuel be eftimated at two fiiillings, and it cannot be pro- 

 bably much lefs, the phofphorus would then coft the manufac- 

 turer about three (hillings an ounce. 



2. If to the acid folution obtained by the above method be The additional 

 added l|lb. of acetiteof lead, value three thiHings, th6 phof- P^^^P^orus ob- 



, , . . t> ' f tamed by addi«g 



phate of lime will be decompofed, and two ounces of phof- acetite of lead, 



phorus fhould be produced from the precipitate, (vide F oar- *^ '^^^^^^ '^^^^P' 



croy.) • This appears then to bean improvement, fince i|oz. 



of phofphorus is procured for three fhillings. But perhaps the 



following procefs may be preferable to either. 



3. To one pound of phofphate of foda, value two fliillings The procefs of 

 and fix-pence; add l|lb. of acetite of lead^ value three ftiil- «^ecompofing 

 lings; above one pound of phofphate of lead will he immedi- byacet! of lead 

 ately precipitated, and about one pound of acetite of foda may affords phofpho- 

 be eafily obtained by evaporation. If this (hoald be valued at^"^ ^'*^* pero». 

 two fliillings and fix-pence, the original coft of the ingredients 



will be reduced to three fliillings, add one ftiilling for fuel and 

 labour, and two ounces of phofphorus will be procured for 

 four {hillings. It is needlefs to remark the great fuperiority of 

 the laft method in point of facility, neatnefs and fimplicicy. 



VII. 



On the Piirifieation of Water hy Filtration ; with the Defcription 

 of a fimple and cheap Apparatus. In a Letter from Si a 

 Henry C. Englefield, Bart. F, R, S, Sfc, 



To Mr. NICHOLSON. 



SIR, 



1 CANNOT but think the filtering machine of Profeifor Obf. on P. Pa> 

 Parrott, publiftied in your laft Journal, a very inconvenient ^achiM ^at/. 

 form of a very common inftrument; but as the filtration of the 



water 



