172 



CONDUCTIVITY AND VISCOSITY IN MIXED SOLVENTS. 



placed at least 2 or 3 cm. from the walls of the bath, to insure uniform tempera- 

 ture; and to render the graduations on the viscometer more clearly visible 



they were filled with India ink, which 

 was then rendered insoluble by heating. 

 The thermometer bulb was always 

 placed between the bulb of the viscometer 

 and the wall of the bath, in order to make 

 certain that that portion of the bath 

 was at the proper temperature. This 

 precaution is necessary, since it was 

 determined by a number of experiments 

 that if any very large amount of water 

 is allowed to collect next to the wall of 

 the bath, its temperature may rise as 

 much as one-half a degree above zero. 

 With a little care, however, it was found 

 possible to keep the portion of the bath 

 immediately surrounding the viscometer 

 constant to within less than one-tenth 

 of one degree. 



The 25 bath was similar to that de- 

 scribed by Jones and McMaster. 1 It 

 was found desirable to place a small 

 quantity of potassium dichromate in this 

 bath, since this not only prevented the 

 accumulation of organic growth in the 

 bath, but also the yellow color made the 

 graduations on the instrument placed 

 in the bath much more clearly visible. 

 This bath was easily maintained con- 

 stant to within one-tenth of a degree, 

 by means of a small flame regulated by a Mohr pinchcock. 



SOLVENTS. 



WATEK. 



The water used was purified as follows : Ordinary distilled water was dis- 

 tilled from potassium dichromate and sulphuric acid. It was then distilled 

 a second time from potassium dichromate and sulphuric acid, into barium 

 hydroxide, from which it was finally distilled into a bottle which was protected 

 from the carbon dioxide of the air and other impurities, by a tube filled 



FIG. 79. 



1 Amer. Chem. Journ., 36, 333 (1906). 



