Conductivities of Some Unusual Salts. 149 



different at 25 after standing in the 25 bath, from the conductivity 

 of the same solution when brought to a temperature of 25 from to 

 15. It was found best to remove the bubbles by tilting the cells 

 slightly and partly removing the electrodes. If this is done once or 

 twice while the solutions are coming to temperature, no further collec- 

 tion of bubbles will be noticed. 



(6) The first few cubic centimeters of conductivity water should be 

 discarded from the siphon used in drawing the water from its container. 

 The water remaining below the stopcock is, to some extent, exposed 

 to laboratory atmosphere, and if some time has elasped since the 

 removal of the last portion, considerable difference in conductivity 

 will be noticed if the above precaution is neglected. 



(c) All connections in the wiring system used with the conductivity 

 apparatus should be soldered where this will not injure the apparatus. 

 When not in use, the ends of the wires for connecting the cells with the 

 bridge should be protected by small glass tubes. 



(d) The noise of the motor used for stirring the baths was found to 

 interfere with the reading of the bridge. This trouble was in a great 

 measure overcome, by mounting the motor on heavy rubber sheeting, 

 and providing washers of the same material for all bolts used in holding 

 this machine in place. 



RESULTS. 



In tables 77 to 94 all conductivities are expressed in Siemens units, 

 and are molecular conductivities gram-molecular weights having 

 been used in preparing the solutions. These molecular conductiv- 



Va 



ities (juJ were calculated from the equation n v = K^r, where K is the 



tib 



cell constant, V the volume concentration, R the resistance indicated 

 on the rheostat, (a) and (6) the two arms of the bridge. The percen- 

 tage dissociation (a) was calculated from the equation a = , where 



Moo 



IJL^ is the highest value of /* obtained. The temperature coefficients 

 expressed in conductivity units were calculated from the formula 



= coefficient 



in which (ju B )k represents /* at the higher temperature fe, and (jujh at 

 the lower temperature (t\) . The coefficients expressed as percentages 

 were calculated from this formula 



For every measurement shown in these tables three bridge readings 

 involving different values for R were made, and the mean of these 

 readings was taken as the basis of calculation. 



