310 ■ PETTERSSON, OK WATER AND ICE. 



centage of sulphuric acid is greater at the snrface of fJie sea tJian 

 at the 'bottom. 



I think the theory »on salt solutions and attached water» 

 published in 1875 by Prof. Gutlirie will best account for the 

 observations enumerated above. Prof. Guthrie found, that 

 every diluted salt solution, on being cooled sufficiently, jdekls 

 up ice, until its temperature reaches a certain point peculiar 

 to the salt, when it solidifies as a whole, maintaining through- 

 out that constant temperature. The proportion of water 

 relatively to the salt in these »cryohydrates» is ordinarily . 

 very large and makes the molecular formulse given to these 

 combinations appear somewhat exuberant to the chemist. 

 This must have induced a short-sighted critic to overlook the 

 importance of the discover}' of Mr. Guthrie, which still 

 affords the only starting-point for an acceptable theory of the 

 origin of the sea-ice. 



»Bearing in mind the existence of the cryohj^drates, cer- 

 tainly of sulphate of magnesium and doubtless also of chloride 

 of calcium (?), at temperatures not far below 0° C, a rapid fall 

 of temperature may be accompanied by more complex pheno- 

 mena of gelation; for if the ice be quickly removed from a 

 large mäss of water by freezing, the resulting brine may easily 

 be so enriched, as to throw out one or more crj^ohydrates, 

 which thus perpetuate in situ a definite amount of saline 



matter The saltness of a floe depends not only upon its 



age hut also upon the rapidity, with which it was at first 

 formed and upon the lowest temperature, to which it bas 

 subsequently been exposed.» 



We will leave the question of the appropriate chemical 

 formula of the cryohydrates aside and listen to some simple 

 facts, told US by Prof. Guthrie, about the freezing points and 

 the chemical composition of some of the cryohydrates, which 

 can possibl}' arise from the freezing of sea-water. 



solidifies at 



— 22° C 



— ir.4 c 



— 37°. o C 



— 5°.o C 



— 0°.- C 



According to this table we ought to expect, that the cryo- 

 hydrate of Na2S04 



4.55 % of NasSOi + 95.45 % of Ho O 



