VOL XXXIIf.] PHILOSOPHICAL TRANSACTIONS. 5 



you will have §iv of salt of tartar. While this salt is yet hot let it be well 

 pulverized, and let there be added to it giv of bullock's blood thoroughly ex- 

 siccated, and reduced to a fine powder. Having mixed them well together, 

 put them into a crucible, so that a third part of it may be left empty. After 

 applying a lid* to the crucible, let it be placed in the fire, surrounded with 

 coals, and be gradually heated, so that the contents may be kindled into a 

 flame, but not too violently. Let the materials be kept in this degree of heat 

 until the flame and combustion abate ; after which let the fire be increased 

 until the matter in the crucible becomes red hot, and scarcely emits any more 

 flame. Then take the crucible out of the fire, empty its contents into a mortar, 

 and reduce them to a fine powder; having at hand 4lb. of rain water, made 

 boiling hot, into which the pulverized materials, while they are yet hot, are to 

 be thrown, and to be boiled therein for the space of -^ an hour. The decoction 

 is to be strained through a linen cloth, and upon the black residuum is to be 

 poured a fresh quantity of water, to be again boiled and strained. This is to 

 be repeated until the water ceases to acquire any saline [or lixivial] taste. All 

 the moisture which is retained by the residuum left on the strainer is to be 

 squeezed from it ; the different decoctions are then to be mixed together, and 

 the collected liquor is to be placed on the fire, and to be evaporated until it is 

 reduced to 4lb. It is then to be kept for use, and marked N° ]. 



In the next place, take of English vitriol -f- slightly calcined:}: to whiteness §j. 

 Dissolve it in §vj. of rain water, filter it through blotting paper, and let it be 

 marked N° 2. 



Lastly, take of crude alum §viij. Dissolve it in 4lb. of boiling water, and 

 when the solution is completed pour it into a sufficiently capacious broad earthen 

 vessel, and mix with it the vitriolic solution N" 2, made boiling hot, and the 

 lixivium N" 1, likewise of a boiling heat. [The vitriolic solution and the 

 lixivium to be boiled in separate vessels.] A great ebullition [effervescence] 

 will instantly take place, and a colour resembling that of mountain-green, or 

 chrysocolla, will be produced. At different times during the ebullition, or 

 effervescence, the mixture should be poured from one vessel into another ; and 

 when the effervescence is over, the liquor should be left at rest. It should 

 afterwards be poured out upon a linen strainer, that all the water may run off, 



* Either not fitting tight, or being provided with an aperture to give exit to the flame during 

 the combustion and calcination of the matter contained in the crucible. 



f Green vitriol, or vitriol of iron. 



+ Exposed to a gentle heat, and only for a short time, so as to be exsiccated rather than calcined ; 

 for by calcination, in the proper acceptation of the term, vitriol of iron is converted into a red 

 powder. 



