156 Intelligence and Miscellaneous Articles. 



lent of Pb (N0 3 ) 2 in aqueous solution is mixed with a solution 

 of an equivalent of KC 2 H 3 2 , to 2 o °f ** are decomposed to 

 KN0 3 , which may be precipitated by adding alcohol, while 

 r §Q- of it remained unchanged " (Storer's ' Dictionary of 

 Solubilities '). Such a mode of experiment is of necessity 

 powerless to give any idea whatever of the equilibrium exist- 

 ing in the solution, for that is at once destroyed by the addi- 

 tion of alcohol. Equally fallacious is any argument from the 

 fact that now one salt and now another crystallizes out from 

 a solution ; for here, too, the equilibrium is being incessantly 

 disturbed by the gradual removal of the w T ater, or the changes 

 of temperature to which the solution is subjected. 



I may sum up my results as follows : — 



When the salt-solutions are mixed, the tendency is to form 

 the system which will occupy the smallest volume (state of 

 stable equilibrium) ; only two salts will then be present in the 

 solution. Under cert-pin conditions, however, when the solu- 

 tions are strong, or where from any cause one of the four 

 possible salts is near its saturation-point, the above may not 

 hold good ; but then a certain amount of the least soluble (or 

 most soluble) salt will be present in the solution, necessitating 

 the presence of all four salts. 



XXI. Intelligence and Miscellaneous Articles. 



ON THE PROPERTIES OF WATER AND ICE. 

 BY OTTO PETTERSSON. 



r PHE above is the title of a valuable paper by Dr. Pettersson, taken 

 -*- from volume ii. of the results of the Vega Expedition. It is de- 

 voted to a discussion of the physical properties of water in the liquid 

 and solid states at the temperatures to which water and ice are exposed 

 in the Arctic Sea, as between — 20° C. and + 15° C. The special 

 subjects investigated were the change of heat and volume of (1) 

 pure water, (2) brackish water, and (3) ocean-water of ordinary 

 saltness ; but before detailing the results of his experiments the 

 author states briefly the results reached by others, and then in 

 detail the instruments employed by him and his methods of obser- 

 vation. In regard to the experiments with pure water, a series of 

 tables gives the results of the experiments on the expansibility of 

 pure water (ice) at the different temperatures employed. The most 

 important point brought out in them is this — that the volume of 

 ice, even the purest which can be tested, decreases with a rise in 

 temperature when near the melting-point, and this is the more 

 marked as the amount of salt contained in the water increases. In 

 regard to this the author remarks that "it is impossible to decide 



