﻿Experiments with Carbon Dioxide in the Solid State. «Sl 



tlie four outer circles show by their imperfection the develop- 

 ment of the circle from the two points that are formed by a 

 double-refracting crystal. 



Authorities. 



ITooke. — Micrographia. 1664. 



GitiMALDi. — Physico-mathesis de lumine, coloribus, et iride. Bologna, 



1665. 

 Huygkns. — Traite" de la Lumiere. 1690. 



Fraunhofer. — Neue Modifikation des Lichtes, &c. Munich, 1823. 

 Fresxel. — Diffraction. 1818. 



Schwerd. — Die Beugungserscheinungen. Mannheim, 1835. 

 Brewster. — Encycl. Brit. 8th ed. 1858 ; art. Optics. 

 Airy.— Undulatorv Theory of Optics. 2nd ed., 1877. 

 Rayleigh. — Encycl. Brit. 9th ed., art. Wave Theory. 



VI. Oil some Experiments with Carbon Dioxide in the Solid 

 State. By Dr. L. Bleekrode*. 



~\T7"HEN working of late with very low temperatures pro- 

 H duced by evaporating solid carbon dioxide I met 

 with some facts which are perhaps not generally known, and 

 may I think prove useful for lecture experiments. 



1 obtained the solid substance in the usual way from its 

 liquid state, now so easily to be had in large quantities in the 

 iron bottles prepared for industrial purposes. If a cloth 

 bag (first used by Bianchi in 1870) is tied to the delivery- 

 valve, the solid may be readily collected inside, and this 

 method is as effective and more simple than the use of ebonite 

 or metal boxes, which are liable to have their parts frozen 

 together and then cannot be quickly emptied. 



Compressed Carbon Dioxide. — This substance on being re- 

 moved from the bag presents itself in a very divided state and 

 therefore evaporates comparatively quickly ; but on submitting 

 it in suitable moulds of wood or metal to high pressure, either 

 by hammering, or still better with screw and lever (as for 

 instance the arrangement for regelation experiments with ice), 

 a most compact substance is obtained, in the form of 

 cylinders, disks, lenses, cups, &c. that can much longer endure 

 the heating-effect of surrounding air. 



Such compressed cylinders were described by Prof. 

 Landolt in 1884f; he obtained them by hammering the 

 mass together ; the specific gravity of the carbon dioxide in 

 that condition was determined, first by calculating the 

 volume of the cylinder from the geometrical dimensions, and 



* Communicated by the Author. 



t Landolt, Chemische Berichte, 1884, xvii. p. 309. 



Phil. Mag. S. 5. Vol. 38. No. 230. July 1894. G 



