1869.] Rubies, Sapphires, Diamonds, and some other Minerals. 299 



more than its normal bulk, even perhaps to the extent of one-fifth or one- 

 fourth. Moreover, in the case shown in fig. 1., the liquid expanded so 

 as to fill the cavity at about 30° C. ; and yet it can be heated up to 42° 

 without bursting it, though, even if the expansion did not continue to 

 increase, and were the same for each degree as from 31° to 32°, the normal 

 volume would be about four times that of the cavity, — which in any case 

 seems only to be explained by supposing that its elasticity is .most remark- 

 ably great, more like that of a gas than of a liquid. There was no decided 

 evidence of its passing into a gaseous state, as does occur when cavities con- 

 tain a less amount of liquid. 



Simmler * has shown that the physical properties of the liquid in topaz, 

 as observed by Brewster, agree more nearly with those of liquid carbonic 

 acid than with those of any other known substance. Dana, in his ' Minera- 

 logy ' (5th edition, 1868, p. 761), calls it Brewsterlinite, and says that its 

 composition is unknown. The facts at Simmler's command were not in all 

 respects satisfactory — since the amount of expansion given by Brewster 

 was from 10° to 26°*7 C, whereas that of liquid carbonic acid observed by 

 Thilorier was from 0° to 30°, and, as shown above, the expansion in- 

 creases so much as the temperature rises that the average rate for 1° is 

 very indefinite. The only reliable method is therefore to compare the ex- 

 pansion between equal degrees of temperature. According to Thilorier f 

 liquid carbonic acid, when heated from 0° to 30°, expands from 100 to 145. 

 One of the experiments described above showed that the liquid in. sapphire 

 expands from 100 to 152; and the other from 100 to 150, which is the 

 most reliable. This agrees so closely with the expansion of liquid carbonic 

 acid, that the difference might easily be due to a slight error in the ther- 

 mometers. The expansion of ordinary liquids is not to be compared with it, 

 nor is that of liquid sulphurous acid. Dr. Frankland has kindly ascer- 

 tained this fact, with special reference to the case in question, and found 

 that from 0° to 32° C. the expansion was only from 100 to 104*36 instead 

 of to 217. 



According to Andreeff £ the expansion of liquid nitrous oxide is not 

 much inferior to that of liquid carbonic acid, being, from 15° to 20°, "00872 

 for each degree, which differs decidedly from that of the liquid in sapphires. 

 The occurrence of nitrous oxide in minerals is also so very much more im- 

 probable, that, on the whole, it seems as if we should be justified in con- 

 cluding provisionally that it is liquid carbonic acid, which, like water, should 

 therefore be classed amongst natural liquid mineral substances. 



Brewster has shown § that when cavities in topaz contain less than one- 

 third of their volume of the expansible liquid, it does not expand when 

 heated, but passes entirely into the state of a compressed vapour. Un- 



* Pogg. Ann. vol. cv. p. 460. 



t GinehVs Handbook of Chemistry, Cavendish Society's Translation, vol. i. p. 225. 

 % Liebig's Ann. vol. ex. p. L 

 § Trans Roy. Soc. Edin. vol. x. p. 25. 

 VOL. XVII, Z 



