26o SCIENCE PROGRESS 



The importance of accurate weighing was insisted upon by 

 most Muslim alchemists, though the exact form of balance 

 they used is not described in any of the manuscripts which I 

 have read. Al-Khazini's hydrostatic balance and the deter- 

 minations of specific gravity he carried out therewith have 

 been described by Bolton. Al-Khazini himself says, " The 

 advantages of the hydrostatic balance are (i) exactness in 

 weighing ; this balance shows variations to the extent of a 

 mithqal [a small weight], although the entire weight be a thou- 

 sand mithqals, provided the maker has a delicate hand, attends 

 to the minute details of the mechanism, and understands it ; 

 (2) that it distinguishes pure metal from its counterfeit, each 

 being recognised by itself without any refining ; (3) that it 

 enables one to know the constituents of a metallic body without 

 their separation from one another ; (4) that it shows the 

 superiority in weight of one of two metals over the other in 

 water, when their weight in air is the same, and conversely ; 

 (5) that it makes the substance of the thing weighed to be 

 known by its weight." 



The table of weights commonly employed was : 



Another table is : 



(This is even more complicated than the English system !) 

 Change of weight during a chemical reaction was not observed, 

 or at least was not considered to be of much importance. 



Apparatus. — Abu Bekr ibn Zakariyya ar-Razi (died about 

 A.D. 900) gives a list of apparatus necessary for the practice 

 of alchemy, of which the following items are typical : 



(i) Furnace. (5) Ladle. 



(2) Bellows. (6) Shears, 



(3) Large crucible. (7) Pestle. 



(4) Smaller crucible. (8) Cauldron. 



