merwin: thermal dehydration of stilbite 



495 



50O" 



400 



CuSO^.SHoO (Fig. 1, B) loses 2 and 2 molecules of water readily 

 and then 1 molecule at a much higher temperature. At 25° the 

 vapor pressure at which both the 5- and the 3-hydrates can 

 exist is about 7 mm. of mercury; and the 3- and 1-hydrates, about 

 4.7 mm.; for the 1- and 0-hydrates, about 0.8 mm.^ 



Stilbite (fig. 

 I, A) loses wa- 

 ter continuous- 

 ly without the 

 least evidence 

 of a break. 

 Ten-minu t e 

 periods of heat- 

 ing gave a curve 

 of the same 

 general shape 

 slightly below 

 this one. The 

 total loss on ig- 

 nition was 17.6 

 per cent. 

 ■ MgS04.7HoO 

 (fig. 1, D) shows 

 four distinct 

 periods of max- 

 imum evolution 

 of water ; the 

 last three repre- 

 sent one mole- 

 cule each. The 

 first one, during 

 which 4 mole- 

 cules of water were lost, may indicate the decomposition of the 

 7-hydrate direct to the 3-hydrate; or intermediate hydrates 

 which decompose immediately may be formed. Such inter- 

 mediate hydrates, all having about the same vapor pressure, are 



300 



200 



lOO 



Fig. 1 



2 Foote, H. W., and Scholes, S. R., Journ. Am. Chem. Soc, 33: 1324. 



