THE 



AMERICAN JOURNAL OF SCIENCE 



[FOURTH SERIES.] 



Aet. I. — The Thermodynamic Relations of Hydrated Glass /* 



by C. Bakus. 



1. Fukther treatment of the fusible water-glass described in 



the preceding communicationf has brought out the following 



points: During the first or opaque stage of the reaction of 



v 

 hot water on glass (200°), volume-contraction (-=. ) and increase 



of compressibility (/9) are both marked phenomena. During 

 the second stage the water-glass becomes more and more clear 

 and limpid. Yolume-con traction falls off asymptotically to 

 zero. Compressibility, after passing through a pronounced 

 maximum which may be even larger than 500/10 6 per atmos- 

 phere, diminishes with great rapidity to the probable isothermal 

 value for pure water (about 100/10 6 ). The relation of change 

 of compressibility to the corresponding volume-contraction 

 (per unit of volume, cold), i. e. d (f/(d v/v ), remains throughout 

 of nearly the same order, lying within an interval of 10/10 6 to 

 20/10 6 , and nearer the former limit so far as measurable. 

 The total apparent volume-contraction of the hot column of 

 water-glass may reach 30 per cent. 



2. On cooling bubbles appear in the clear water-glass in great 

 number, showing it to contract on solidifying from the center 

 outward (centrifugally), like a Prince Rupert drop. The solid 

 water-glass is in appearance as hard and brittle as ordinary glass, 



*Read before the Nat. Academy of Sciences, Nov. 16th, 1898. 



fThis Journal (4), vi, p. 270, 1898; cf. this Journal (3), xli, p. 110, 1891. The 

 experiments of this paper ending with compressibilities as high as 200/10 6 , relate 

 chiefly to the opaque stage. 



Am. Jour. Sci.— Fourth Series, Vol. VII, No. 37.— January, 1899. 

 1 



