On Ice and Brines 131 



who have confined their observations to the laboratory have 

 concluded that the ice formed when saline solutions of 

 moderate concentration, including sea-water, are frozen, is 

 pure ice, and the salt from which it is impossible to free it 

 entirely belongs to the mother-liquor, while those who have 

 collected and examined sea-water ice in high latitudes have 

 come to the opposite conclusion. 



During the Antarctic cruise of the " Challenger " I made 

 a number of observations on the sea-water ice found in those 

 regions, and, relying principally on the fact that the melting 

 temperature of the ice was markedly lower than that of fresh- 

 water ice, and that it was impossible by any of the ordinary 

 means familiar to chemists for freeing crystals from adhering 

 mother-liquor to materially reduce its salinity, I came to the 

 conclusion that the ice formed in freezing sea-water is not a 

 mixture of pure ice and brine, but that it contains the salt 

 found in it in the solid state either as a crystalline hydrate or 

 as the anhydrous salt, but most probably as a hydrate. In 

 dealing with the subject, Dr Otto Pettersson ( Water and Ice, 

 p. 302) quotes my observations, and also rejects the view 

 that " sea-ice is in itself wholly destitute of salts, and only 

 mechanically incloses a certain quantity of unfrozen and 

 concentrated sea-water." He founds his belief on the fact 

 that numerous analyses of specimens of sea-water ice have 

 shown that the constitution of the saline contents of different 

 specimens of ice differs for each specimen, and is always 

 different from that of the saline contents of sea-water. Were 

 the salinity due to inclosed unfrozen and concentrated sea- 

 water, we " ought to find by chemical analysis exactly the 

 same proportion between Cl, MgO, CaO, SO 8 , etc., in the 

 ice and in the brine as in the sea-water itself." He quotes 

 numerous analyses of specimens of sea-water ice from the 

 Baltic and from the Arctic Seas to show that this is not the 

 case. Calling the percentage of chlorine in each case 100, he 

 found in various sea-waters the percentage of SO 8 to vary 

 from 1 1*49 to 11-89. I" specimens of sea- water ice it varied 

 from I2'8 to 76*6, and in brines separating from the ice and 

 remaining liquid at 30 C. it varied from 1*14 to ri6. 



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