MR J. Y. BUCHANAN ON THE 



PAGE 



maintenance of a, constant temperature in the laboratory requires careful study, details 

 of wliich, Avith examples, are given. The room used as laboratory should be of moderate 

 dimensions, because it is to be occupied only by the experimenter, who must have 

 absolute control over it. It should be illuminated by the light of the northern sky, 

 and the direct rays of the sun must be absolutely excluded. When these primary con- 

 ditions are given, the experimenter must do the rest. 



SECTION V. 

 Tables. 



26. A. General Tables Nos. 1 to 37, giving, the facts of observation. 61 



27. B. Tables Nos. 38 to 61, giving particulars relating to the exactness of the determinations 73 



of the specific gravity given in Tables A, in cases in which two hydrometers were used. 



28. C. Tables Nos. 62 to 71, giving a summary of the specific gravity of the solutions of 80 



different salts at different temperatures. 



29. D. Tables Nos. 72 to 81, giving a summary of the increment of displacement, v, caused 84 



by the dissolution of ?n gram-molecules of salt in 1000 grams of water at different 

 temperatures. 



30. E. Tables Nos. 82 to 91, giving the values of v/m, that is, the mean increment of dis- 89 



placement calculated for the dissolution of 1 gram-molecule of salt in 1000 grams of 

 water at different temperatures. 



31. A. Tables Nos. 92 to 103, giving the facts of observation for strong solutions. 94 



32. Tables Nos. 104 to 124, of the Classes C, D and E, for strong solutions, 98 



SECTION VI. 



General Description of the Tables. 



33. Explanation of symbols in tables of Class A. With the exception of the determination 100 



of temperature, the result of every series of observations depends only on determina- 

 tions of weight, and is independent of the work of others. The necessity for study 

 and practice before the experimenter can be confident of his power to control the tem- 

 perature of the solution and of the laboratory is insisted on. Failure to appreciate this 

 has interfered with the general use of the hydrometric method. 



34. The measure of the displacement of a body having the temperature T is the weight of dis- 101 



tilled water having the temperature T which the body displaces when totally immersed 

 in the water. Under this definition the unit of displacement is the space occupied by 

 1 gram of water at T. The symbol for the unit of displacement is G^ or G^ , in which G 

 represents 1 gram, and T or f the common temperature of the body and of the water 

 displaced by it. When the unit of weight is the kilogram, the unit of displacement is 

 expressed by the symbol K,p or K(. The eff'ect of concentration on the displacement 

 produced by dissolving a given amount of salt in water or in solution is pointed out. 

 Dilution of solutions for which m is > 1/8 produces contraction ; when m is less than 

 1/16 expansion occurs in many cases. This could not have been ascertained except by 

 the liydrometric method. 



