74 



Studies on Solution. 



The viscosity measurements were obtained in a modified form of 

 the Ostwald viscosimeter, the diameter and length of the capillary 

 being adjusted so as to render the instrument suitable for measuring 

 liquids more viscous than water. The viscosimeters were calibrated 

 according to the more accurate method proposed by Thole, 1 using as 

 calibrating liquids ethyl, propyl, and isobutyl alcohols, 30, 40, and 50 

 per cent by weight mixtures of ethyl alcohol and water and a 40 per 

 cent solution of pure sucrose. The values for the density and viscosity 

 of these calibrating liquids were obtained from the data compiled by 

 Thole, Bingham, 2 and others from the most reliable measurements of 

 various investigators. The average constant obtained for each instru- 

 ment with this method gave somewhat larger values for the viscosity 

 of formamid solutions than when calibrated with water alone, the time 

 of flow of water being too short for accurate measurements i. e., 

 less than 100 seconds. The following will serve as an example of the 

 constants obtained : 



Viac.'OSIMETEH I.\. 



All measurements, both of conductivity and viscosity, were carried 

 out in the thermostats described in a previous paper, in which a con- 

 stant temperature to within 0.01 was maintained. 



In order to obtain completely anhydrous samples of the salts studied 

 a vacuum drying-oven was designed and constructed with the aid of 

 Dr. Pardee. This apparatus consisted of a tubulated bell-jar 18 cm. X 

 24 cm. mounted on a heavy iron vacuum-plate. Two pairs of electrical 

 connections lead into the center of the plate through a rubber stopper, 

 one pair to a stove consisting of a 50-watt carbon-filament lamp incased 

 in a metal chimney open at the top and having a circular window near 

 the bottom, the other pair leading to a miniature fan motor in series 

 with an 8 candle-power carbon lamp placed on the outside base. The 

 fan maintained circulation within the oven by driving the air through 

 the open side of the chimney, up around the lamp, and then out over 

 two dishes containing either sulphuric acid or phosphorus pentoxide. 

 The material to be desiccated was placed in watch crystals on per- 

 forated trays set above the motor and chimney. The tubular in the 



'Journ. Ohem. Soc., 105, 2009 (1914). 



"Zeit. Phys. Chem. 83, 044 (1913); Bureau Standards Scientific Paper No. 298. 



