[ 144. ] 



XVIII. On the Density of certain Substances {Quartz, Corundum, 

 Metals, &;c.) after fusion and rapid cooling. By M. Ch. 

 Sainte-Claire Deville*. 



IN the Comptes Eendiis, vol. xx. p. 1453, I communicated the 

 results of some experiments which establish a notable dif- 

 ference between the density of certain crystallized minerals and 

 that of the vitreous bodies obtained by subjecting those minerals 

 to fusion and rapid cooling. I have thus shown that these 

 differences, referred to the primitive density of the crystallised 

 mineral, were, — 



For a labrador .... 0-06 



For a felspar 0-08 



For a hornblende . . . 0"13 

 For an augite .... 0"14 

 For a vesuvian . . . . 0'16 



From which it may be inferred reciprocally, that, in the act of 

 crystallization, a very remarkable concentration of matter to a 

 maximum of density takes place in these substances. 



All these minerals are silicates : it was therefore natural to 

 inquire whether the same effect would show itself with crystal- 

 lized silica or quartz. 



That this is the case I have been able to assure myself, 

 through the obliging assistance of M. Gaudin, who has been kind 

 enough to place at ray disposal a simple and ingenious apparatus 

 by means of which he obtains a very high temperature. I have 

 been thus able to obtain with the greatest facility hyaline quartz 

 melted into small drops, or in lumps. 



I have carefully determined in the first instance the density of 

 the quartz itself t; here are the mmibers which I obtained: — 



1. Fine crystal of quartz, perfectly colourless 3i^tl~l „ o«„ 

 transparent j 



3. Quartz extracted from a granite of a medium! q.^^q 

 grain J 



3. Quartz from porphyry, composed of quartz and^ q.cftQ 



felspar only J 



4. Quartzdistributedinanirregularmannerinarockl 



of Guadaloupe, with labrador, and apparently >2"653 

 formed by concretion (mean of four experiments) J 



Mean .... 3-656 



* Comptes Rendiis, vol. xl. p. 769. 



t The densities cited in this note ai-e taken for the most part with powder 

 of a uniform grain obtained by means of two sieves, rejecting what passed 

 through the finest and what remained ujion tlie coai'sest. All the numbers 

 aie referred to water at its maximum density. 



J 



