On the Viscosity of Calcium Chloride Solutions. 95 



It' this reading were excluded there is a difference in the 

 grand means of about one part in 13,000 — the rotation in 

 the case o£ the spark being the less. Since this is within 

 the possible error of the experiment, the final result may be 

 stated by saying that so far as these experiments go there is 

 no certain indication of a directive action of light upon the 

 molecules of the sugar in solution. 



University College, 

 London. 



VIII. On the Viscosity of Calcium Chloride Solutions. By 

 Frederick Simeon, B.Sc.< Physics Research Scholar, Uni- 

 versity of London, University College *. 



WHILE the present work was in progress, an account 

 of work on the same subject was read before the 

 Physical Society of London by Mr. Tucker f. However, so 

 much of the present work had been done, and the apparatus 

 in use differed in so many respects from that used by 

 Mr. Tucker, that it seemed well to proceed until a com- 

 parison of results could be made. 



The apparatus employed was identical in principle with 

 that used by Thorpe and Rodger J. It consisted of a hori- 

 zontal capillary tube, about 30 cm. long and 0*4 mm. in diam., 

 connected to two vertical tubes about 18 cm. long and 1 sq. cm. 

 cross-section. A fixed quantity of the liquid whose viscosity 

 was to be determined was forced through the capillary tube 

 under constant pressure from one upright tube to the other, 

 and the time of passage carefully observed. The apparatus 

 was immersed in a large bath of water at constant temperature 

 until the lines on the upright tubes which determined the 

 volume of liquid transmitted were just visible above the edge 

 of the bath. 



At least six, and usually eight to twelve readings of the 

 time of passage, which did not vary by more than about 

 0'2 per cent., were made for each solution. 



The coefficient of viscosity is calculated from the ratio of 

 this time to the corresponding time for pure water, assuming 

 the values for water found by Thorpe and Rodger. The 

 times of passage in opposite directions differ by a very small 

 amount due to slight asymmetry in the apparatus; but, in 

 practice, the times in opposite directions were kept separate. 

 and thus two values for the ratio of viscosities were found 

 which agreed very closely. 



* Communicated by Prof. A. W. Porter, F.R.S. 

 f Proc. Pliys. Soc. vol. xxv. p. 111. 

 t Phil. Trans. 1894, A. p. 1. 



