52 Scientific Proceedings, Royal Dublin Society. 



furnished with a wide median vertical perforation parallel to the two pine 

 rods. When the pine supports are placed in the small test-tubes, the metal 

 rod is passed tlirough the perforation in the connecting-piece, and works 

 loosely in it. Before fixing in the connecting-piece the pine supports are 

 thorouglily impregnated with paraifin-wax by keeping them submerged for 

 some time in melted wax near its boiling-point. The junctions and the wires 

 coming from tliem are laid along the supporting rods thus j^repared and 

 fixed in the connecting- piece, and are bound to the rods, and the whole is 

 waterproofed and insulated with several coats of collodion varnish. The 

 supporting rods are continued above the connecting-piece and are produced 

 through corresponding perforations in the upper bung {d), in wliich the rods 

 fit loosely. It is convenient that some kind of easily detached stop [q) 

 should be fixed on one of the rods above the upper bung to prevent the 

 rods slipping out of tliis bung when the test-tubes are removed. The copper 

 leads (/) emerge from the freezing-chamber along one of the supporting rods. 



This arrangement, which will be easily understood by reference to fig. 1, 

 allows the junctions in each of the smaller test-tubes to be simultaneously 

 moved by raising and lowering the upper ends of the pine supports, when 

 the upper bung is in position and the freezing-chamber is closed. The 

 double lead is easily introduced, or withdrawn at will, from the perforation in 

 the upper bung by means of a narrow slit opening into that perforation from 

 the side of the bung. 



From these arrangements it will be seen that the method has been 

 rendered a comparative and differential one, and consequently it might be 

 thought that corrections necessary for the thermometric methods may be 

 partly or wholly dispensed v?ith here. This is in part at least true, as will be 

 understood from a consideration of tlie formula which Nernst and Abegg 

 have introduced embodying the corrections necessary in the thermometric 

 method. It is 



To is the "true" freezing-point of the solution under examination; t' is 

 the observed temperature (i.e. the reading of tlie thermometer) ; to is the 

 so-called " convergence-temperature," i.e. the temperature which the solution 

 tends to take up due to its loss of lieat to the freezing-bath and its gain due 

 to the stirring. This temperature depends on the heat-capacity, the con- 

 ductivity, the size of the vessel and its contents, and also on the rapidity of 

 the stirring and on the friction in the solution. 



' Quoted from Osmotisclier Druck- und lonenlehre. H, J. Hamburger. Wiesbaden, 1902, vol. i., 

 p. 66. 



