abstracts: physics 521 



result. These considerations serve to show that there may in certain 

 cases be difficulties in the way of always being able to reproduce a given 

 result; in order to do this in any case, it is necessary to control carefully 

 the amount of water relative to the volume of the containing vessel 

 (the degree of filling), the temperature, and, if possible, the pressure 

 also. The critical point of water is only a secondary factor in deter- 

 mining the nature of the product, its influence being effected principally 

 thru the change in concentration of the solvent (liquid or fluid) in the 

 neighborhood of the critical point. 



The thoro investigation of hydrothermal syntheses is beset with many 

 difficulties, apart from the technical problems inherent in operating on 

 heterogeneous systems within closed bombs at high temperatures. 

 Nevertheless our knowledge of the real relationship of these minerals 

 can be advanced materially if care is taken to control the factors in- 

 volved, the most important of which are the initial composition of the 

 system (including therein the relation between the amount of water and 

 the volume of the bomb) and the temperature. G, W. M. and P. N. 



PHYSICS. — Densities at high temperatures. Arthur L. Day, R. B. 

 SosMAN and J. C. Hostetter. Am. Jour. Sci. (4). 1913. 



The existing and rather conflicting data on the volume change of 

 rocks on fusion are reviewed briefly. A method and apparatus is de- 

 scribed for the determination of the specific volume of metals or of solid 

 or fused silicates from 200° to 1600°. The basis of measurement is the 

 expansion of artificial graphite, which was determined from 20° to 1500°. 

 Volume curves are given for tin, lead, and the eutectic of lead and tin. 

 Measurements were made on quartz up to 1600°. The volume of 

 quartz increases more and more rapidly as 575° is approached. At this 

 point the inversion takes place to the high-temperature form, whose 

 volume decreases slightly with rising temperature. Between 950° and 

 1250° gasses are given off. Above 1300° the volume is increased greatly 

 by the formation of cristobalite. Granite shows the same form of curve 

 as quartz. Above 500°, however, it is not possible to obtain its true 

 volume expansion because of the shattering and permanent dilation due 

 to unequal expansion of the minerals and to escape of gasses. The same 

 is true of crystalline diabase. 



The curve of glassy diabase can be obtained, however. The glass 

 crystallizes with contraction of volume at about 900°, then begins to 

 fuse again at about 1 150°. On cooling, the liquid again crystallizes with 

 contraction. This behavior explains completely the results of Barus, 



