DISCUSSION OF EVIDENCE. 143 



the only reasonable suggestion which will account for them, to show 

 that the suggestion is true. 



Aided by a grant from the Carnegie Institution of Washington, I 

 started Dr. Getman 1 on a more or less systematic study of the whole 

 problem. The question arose, were the results already obtained 

 limited to a few compounds, or types of compounds, or was this a 

 general phenomenon? We took up the study of acids, bases, and salts 

 in concentrated solutions, especially by the freezing-point and conduc- 

 tivity methods. We also studied the refractivities of many solutions. 



RELATION BETWEEN LOWERING OF THE FREEZING-POINT OF WATER AND WATER 

 OF CRYSTALLIZATION OF THE DISSOLVED SUBSTANCE. 



The work of Getman included the study of the lowering of the freez- 

 ing-point of water produced by concentrated solutions of the chlorides 

 of sodium, potassium, ammonium, lithium, barium, strontium, cal- 

 cium, magnesium, iron, and aluminium; the bromides of sodium, 

 potassium, lithium, barium, strontium, calcium, magnesium, and cad- 

 mium; the iodides of sodium, potassium, lithium, calcium, barium, 

 strontium, and cadmium; and the nitrates of sodium, potassium, 

 ammonium, lithium, calcium, magnesium, manganese, cobalt, nickel, 

 cadmium, zinc, aluminium, iron, and chromium. The relation between 

 lowering of freezing-point and water of crystallization can be seen very 

 well from the curves. 2 



The nitrates of sodium, potassium, and ammonium, which crystallize 

 without water, produce the smallest lowering of the freezing-point of 

 water. Then come the nitrate of lithium with 2 molecules of water, 

 calcium with 4, and a large number of nitrates each with 6 molecules 

 of crystal water; all give about the same lowering of the freezing-point. 

 Finally, the three nitrates of aluminium, iron, and chromium with 8 

 and 9 molecules of water, give the greatest lowering of the freezing- 

 point of water. 



Relations similar to the above come out for the chlorides, the 

 bromides, and the iodides. 3 The freezing-point lowerings of water 

 produced by them are roughly proportional to the amounts of water 

 with which the salts crystallize. 



If, on the other hand, we compare the chlorides with the bromides, 

 with the iodides, with the nitrates, similar relations manifest themselves. 



It was found that chlorides, bromides, iodides, and nitrates which 

 have no water of crystallization, all produce about the same molecular 

 lowering of the freezing-point of water, and this is between 3 and 4. 



'Amer. Chem. Journ., 27, 433 (1902) ; 31, 303 (1904) ; 32, 308 (1904) ; Zeit. phys. Chem., 46, 244 

 (1903); 49, 3S5 (1904); Phys. Rev., 18, 146 (1904); Her. d. chem. Gesell., 37. 1511 (1904). 

 2 See Carnegie Inst. Wash. Pub. No. 60, p. 24. 

 3 See Carnegie Inst. Wash. Pub. No. 60, pp. 20-26. 



