CROOKES' DECIMALS. 28l 



The weight of one cubic centimeter of air, at common 

 temperatures and pressures, is 1.2 milligrammes. 



If S is the specific gravity (i. e., grammes per cc), then 

 the specific volume is i divided by S (cc per gramme). 



Hence the weight of one gramme of this substance is 

 buoyed up by 1.2/8 milligrammes. 



The brass -weights (spec. grav. 8.5) are, therefore, buoyed 

 up by 0.14 milligrammes per gramme. As they are on the 

 opposite pan, it must be subtracted from the buoyancy of 

 the substance weighed. 



For Salt, S = 2.16 gives 1.2/8 = 0.55; corrected for brass 

 weights 0.55 o. 14 = 0.41 . 



For Pyroarsenate S:= 2.30 gives 1.2/8=0.52; corrected 

 for brass weights, 0.38. 



These are the minute factors above used. 



In this way, a most simple calculation will quickly show, 

 how many units in the fifth place the absolute atomic ratio 

 will be lowered or raised by the buoyancy of the air. 



No calculations are to be made for each individual 

 determination; only one single and most simple calculation 

 for the entire process. See pp. 64-65. 



If this direction is followed to the letter, there will not 

 be any chance for such deplorable inadvertent mistakes in 

 the reduction to vacuum as have disfigured the work of 

 Stas and his disciples until we lifted the veil of mystery 

 and fraudulent exactitude that has hid them for so many 

 years. 



II. HOW CROOKES MANUFACTURED DECIMALS. 



In the absence of the Philosophical Transactions (see p. 

 122), I supposed that the last three decimals had been 

 " determined " by Grookes by the oscillation method 

 (p. 129). 



Looking at a book in the hands of my son, taken by him 

 from the Mercantile Library, I find it to be Crookes' Select 

 Methods in Chemical Analysis, II edition, London, 1886. 



