20 Day, etc. — Determination of Mineral 



the lowest dilatation coefficients, actually contracting in two 

 directions while expanding in the third.* A great deal of 

 additional work on the properties of matter in the solid state is 

 necessary before these relationships can be understood. 



Escape of gases from, quartz. — As the data of fig. 6 show, 

 there was a rapid escape of gases from the quartz, beginning 

 at about 950° and continuing for a varying period of time 

 depending upon the rate of heating. We made no attempt to 

 find the lowest temperature at which this gas evolution would 

 begin, nor did we study the effect upon the gas evolution of 

 holding the quartz for a long time at a fixed temperature. 



Chamberlinf has found that the average amount of gas 

 obtained from six specimens of quartz was 0*35 of the volume 

 of the crystal, and that the gases consisted chiefly of carbon 

 dioxide and hydrogen. The amount of gas obtained by simply 

 crushing the mineral to open the microscopic cavities was insig- 

 nificant, even from quartz having comparatively large cavities. 

 The amount obtainable by chemical reactions of water and 

 impurities in the quartz was also small. The greater part of 

 the gas seemed therefore to be either in solution in the solid 

 crystal, or held in invisible cracks. 



Our experience supports this view. Quartz heated to 1300° 

 under tin, after giving off a considerable quantity of gas above 

 1000°, was brought back to room temperature with relatively 

 few cracks and with unimpaired transparency. The cracking 

 seems usually due to the rapid volume change as the tempera- 

 ture approaches 575°. 



The volume of gas escaping from our quartz specimens 

 was, however, much greater than the volumes stated by Cham- 

 berlin. It should be noted that the gases collected by Charn- 

 berlin were all passed over calcium chloride before any 

 measurements were made, so that he has no data on the amount 

 of water vapor evolved nor on the temperature at which it 

 escaped. 



A. "W. Wright;}: found that the smoky quartz of Branchville, 

 Connecticut, contained, on the average, O062 per cent water 

 which escaped below red heat, in addition to 1*32 volumes of 

 gas chiefly carbon dioxide.§ This quartz contained unusually 

 large inclusions filled with water- aud liquid carbon dioxide. 

 Koenigsberger and Mueller|| found that 80 to 90 per cent of 

 the included material in three Alpine quartzes was water. 



* Fizeau, Pogg. Ann., cxxxv, 372-395, 1868. 



t K. T. Chamberlin : The Gases in Eocks, Carnegie Institution Pub. 106, 

 1908. 



% This Journal (3), xxi, 209-216, 1881. 



§ Wright's figure has been quoted erroneously as " 0'07 volume" ia 

 Chauiberlin's table (p. 24 of Publication 106). 



| Centralblatt Min., 72-77, 1906. 



