306 BULLETIN OF THE UNIVERSITY OP WISCONSIN. 



ductivity measurements at the higher temperature were made at 

 95° instead of at 100°. The resistance cell was immersed in a 

 large paraffine bath whose temperature was carefully regulated 

 at 95°. 



The freezing-point determinations were made with a regular 

 Beckmann's apparatus of large size, about 40 grams of water 

 being used in each case. The solutions were cooled only from 

 two to three-tenths of a degree below their freezing-points, and 

 the crystallization was each time inaugurated by means of a 

 point of ice. The boiling-point determinations were made with 

 a Beckmann's apparatus of about double the ordinary size. Un- 

 less otherwise stated, appropriate Beckmann's thermometers 

 graduated to 0.01° (made by F. O. R. Goetze in Leipzig) were 

 used. It was at first thought best to surround the thermom- 

 eter with a platinum cylinder in the boiling tube, as recom- 

 mended by Jones, but it was soon found that this at times causes 

 slight fluctuations in the boiling-point, apparently due to the 

 fact that the solution within the cylinder is apt to be slightly 

 more concentrated than that without. 



The water used in the experiments was distilled water con- 

 densed in a block tin condenser. By drawing air freed from 

 carbon dioxide through it for a long time its conductivity was re- 

 duced to 2X10 -6 (or somewhat less) at room temperature. The 

 conductvity of the water has been deducted in each case, after 

 having been determined at the proper temperature. The sub- 

 stances used were all of the C. P. variety of standard makes, 

 generally either Kahlbaum's or Schuchardt's. They were tested 

 as to their purity and as a rule were recrystallized. When the 

 salt contained water of crystallization, the amount of this was 

 ascertained, and the salt was weighed in the crystallized form 

 for the molecular weight determinations, the crystal water being 

 added to the solvent in making the computations, so that the 

 latter are all based on the amount of anhydrous salt in the solu- 

 tions. For the conductivity determinations the appropriate 

 quantities of salt (also calculated on the basis of the anhydrous 

 substance) of course simply had to be made up to the required 

 volume at the proper temperature. 



