﻿290 Mr. C. J. Smith on the Viscosity and Molecular 



and the corrected time o£ fall proved to be 104*70 sees., a 

 value which is probably correct to 0*1 sec. With this time 

 of: fall the corresponding time of fall for carbon oxysulphide 

 has been compared, and with appropriate corrections gives 

 the relative viscosity, from which the absolute viscosity has 

 been obtained by assuming the viscosity of air at 15 o, C. 

 to be 1*799 x 10" 4 C.Gr.S. units. In addition, the variation 

 of viscosity with temperature has been derived from com- 

 parisons of the corrected times of fall at atmospheric and 

 steam temperature. 



Preparation and Purification of the Carbon Oxysulphide. 



The carbon oxysulphide was prepared by the action of 

 sulphuric acid (five vols, acid, four vols, water) on pure 

 potassium thiocyanate in the cold (room temperature). At 

 the same time hydrocyanic acid, formic acid, and carbon 

 bisulphide are formed. To remove these impurities the 

 method recommended by Moissan * was used. This consists 

 In passing the gas through a strong solution of caustic 

 potash to remove the hydrogen cyanide and then over wood 

 charcoal to remove the carbon bisulphide. The gas was 

 dried by being passed over calcium chloride, and then 

 solidified at liquid air temperature. All permanent gases 

 were pumped out of the U-tube containing the solid COS by 

 means of a mercury pump. The liquid air was then replaced 

 by a mixture of solid 00 2 and alcohol at —80° C, when it 

 was observed that the vapour pressure of the liquid COS was 

 about 30 cm. of mercury. The C0 2 mixture was then 

 removed and samples of the gas collected over mercury. It 

 was further purified before being introduced into the 

 viscometer by fractional distillation at liquid air temperature. 

 The liquid air having been replaced by C0 2 and alcohol at 

 — 80° C, it was possible on account of the comparatively 

 high vapour pressure of COS at this temperature to pump 

 off successive quantities of dry COS sufficient io fill the 

 viscometer at atmospheric pressure. 



Experimental Results. (Table I.) 



W^e have -f 15 = 69*96 sees., and £ 100 — 90*64 sees. 

 The ratio of these times of fall gives the ratio of the 

 viscosities at the corresponding temperatures. 

 Thus 



*7ioo _ ^ioo _ 9 0*64 _-,. 9 QKp 

 Vis ~ *i5 69 96 ~ 

 * Moissan, Traite de Chimie, vol. ii. p. 318. 



