16 THE ATOMIC WEIGHTS OF 



The dehydration of this salt was studied more fully by Hoskyns 

 Abrahall, u in 1889. He found that when borax was heated to 

 between 250 and 300 for 20 hours, under reduced pressure, 

 about 0.5 per cent, of water still remained, but that "practically 

 the whole of the water that could be expelled at this temperature 

 came off in the first 3 or 4 hours." 12 It is interesting to note that 

 this chemist condensed all the water given up by a sample of 

 crystallized borax heated to 265 in a vacuum. This water "did 

 not act on turmeric paper and left no appreciable residue when 

 left to evaporate in the cold over sulphuric acid." The crucible 

 containing the borax was then heated over a direct flame, first 

 over a Bunsen burner and finally over the blast-lamp, and in 

 two instances in a small Fletcher furnace capable of melting cast 

 iron. However, AbrahalPs experiments show that, depending 

 upon the mode of heating, appreciable and varying quantities 

 of borax were volatilized ; hence he concluded that the dehydration 

 of borax was untrustworthy for the derivation of an atomic ratio. 

 (See also quotation on p. 52). 



A number of experiments relative to the volatility of borax, 

 upon fusion, were carried out by Waldbott 13 for practical and 

 general analytical purposes. He discovered, for example, that 

 a portion of borax glass, weighing about a gram, lost 14 per cent, 

 when heated over the blast-lamp for 3 hours and that a quantity 

 of fused borax (cir. 12.0 grams), kept in a kiln at about 1400 

 for 60 hours, lost almost 50 per cent, of its original weight. Inci- 

 dentally, it may be mentioned that, from several analyses of the 

 residues, Waldbott drew the conclusion that no segregation takes 

 place during fusion, but that the salt is volatilized as such, i.e., 

 as Na 2 B 4 O 7 . This flatly contradicts Leonard, 14 who states that 

 ' ' the residue contains rather less soda than that required for the 

 formula Na 2 B 4 7 , and that the residue is not constant." 



Waldbott's observations in this particular are probably more 



11 J. Chem. Soc., 61, 650 (1892). The paper was edited and published by Ewan and 

 Hartog. 



"More recently, J. Hoffman (D.Chem. Ind. 39, 411-412 (1917), has studied the pro- 

 gressive dehydration of borax at various temperatures (from below 100 to 318) 

 and finds that the final molecule of water is exceedingly tenacious, according to 

 an abstract published in the J. Chem. Soc. 112, II, 206. 



1J J. Am. Chem. Soc., 16, 410-418 (1894). 



"Chem. N. 77, 104 (1898). 



