﻿82 Dr. L. Bleekrode on some Experiments 



then by ascertaining its weight with the balance, taking care 

 to collect the gas, which evaporated during the process, in a 

 potash solution, connected with a delivery-tube to the vessel 

 containing the solid substance, the whole arrangement of 

 course standing on one of the scales of the balance. In this 

 way the specific gravity was found to be 1'2 (in the liquid 

 state, at 12°"5 C. it is 0*88), and accordingly the larger pieces 

 of the dioxide sink in water ; the smaller ones remaining 

 suspended on the surface owing to the evolving gas. I myself 

 found in different experiments the number 1*3, and even 1*6 ; 

 this greatly depending on the pressure exerted, which, with 

 my apparatus, could be made very high ; at the latter density, 

 the cylinders looked semi-transparent. The great advantage 

 now gained lies in the very slow evaporation. Landolt men- 

 tions that he was able to keep a cylinder with dimensions of 

 25 mm. and 26*8 mm., having a weight of 15*63 grammes, 

 during one hour and a half ; I could maintain one, at a 

 .temperature of the atmosphere of 15° C, having a weight of 

 41 grammes, during nearly the same time ; but he was even 

 able to keep a cylinder of 41 mm. diameter and 53 mm. 

 high during five hours. The surface, as is to be expected, soon 

 becomes covered with ice needles that are easily nipped off, 

 but Landolt is of opinion that a hydrate is also formed. 



Production of Electricity. — It has been remarked by more 

 than one observer that a strong jet of carbon dioxide, obtained 

 from its liquid, on expanding in the atmosphere, may produce 

 an electric charge of marked intensity. Riess in his well- 

 known book on frictional electricity mentions that, as long 

 ago as 1852, Joly saw electric sparks given off by an iron 

 bottle which was filled with liquefied gas ; and also Ducretet 

 at Paris made a communication in 1884, on the appearance of 

 sparks, when he caused the gas to escape from its liquefied 

 state in a box of ebonite, in order to collect the solid substance. 

 More recently Hausknecht * published the same observation, 

 but adds the important remark that it is necessary, when 

 powerful effects are aimed at, to use a gas absolutely free from 

 air, and therefore that prepared by chemical means is better 

 suited for these experiments than that obtained from natural 

 sources, as manufactured on the Rhine. The cloth collecting- 

 bags show an intense electric charge, emitting a violet light 

 inside, and he got sparks of even 20 centim.; but they do not 

 appear before a dense layer of crust of solid matter has been de- 

 posited. I found this confirmed, and after I had insulated the 

 iron bottle on paraffin supports, I applied a delicate gold-leaf 

 electroscope, and ascertained, when gas was strongly issuing, 

 * Chemische Berichte, 1890, xxiv. p. 1032. 



