204 On the Sea Water on the Coasts of France. [Sept. 



A hundred grammes of these different salts exposed for three 

 days to the open air attracted moisture, and were increased in 

 weight to 116 grammes, and this weight was still farther increased 

 by longer exposure. 



This saline residuum was repeatedly digested in alcohol, in order 

 to dissolve the deliquescent salts. We continued the digestions till 

 the alcohol ceased to be rendered muddy by potash, which showed 

 the absence of the deliquescing earthy salts. Boiling alcohol must 

 not be employed ; because it has the inconvenience of dissolving a 

 quantity of the common salt, a part of which indeed crystallizes as 

 the liquid cools. The salts ought to be reduced to a fine powder, 

 otherwise a portion of the deliquescent salts might be left undis- 

 solved. 



The different alcoholic liquids were evaporated to dryness. The 

 drv matter was exposed to the air, and in a few days it deliquesced 

 Into a liqujd. Then two decigrammes (three grains) of common 

 salt were separated from it, and added to the undissolved portion of 

 the salt. The liquids were then again evaporated to dryness, and 

 the residues dried at the temperature of boiling water.* 



The dry residues were then weighed. The following were the 

 results obtained: — 



Water from Dieppe — Muriate of magnesia, 7 grammes. 



Water from Havre — Muriate of magnesia, J grammes. 



Water from Br.yonne — Muriate of magnesia, fr| grammes. 



Water from Marseilles — Muriate of magnesia, 7'3 grammes. 



These different salts, when treated with potash, yielded from 1*3 

 gramme to 16 gramme of magnesia. 



The small quantity of magnesia obtained is a proof that the salt 

 contained too much water. Hence we think it more exact to de- 

 termine the weight of the salt from that of the magnesia dried and 

 calcined. This would indicate for the water of the Channel and of 

 the Atlantic 3 - 5 of muriate of magnesia, and for the water of the 

 Mediterranean 5*25. 



When the residue of the evaporation of a kilogramme (15444 

 grains) of water has been thus exhausted by alcohol and dried, it no 

 longer attracts humidity from the atmosphere. 



We ascertained that this salt dissolved by alcohol contained no 

 muriate of lime. Indeed it is obvious that no such salt can exist in 

 sea water if we attend to the presence of sulphate of magnesia. 

 Muriate of lime when dropped into sea water occasions a precipi- 

 tate when the water has been concentrated to one sixth of its oiigi- 

 nal volume, as we have ascertained by experiment. The salt dis- 

 solved by the alcohol is pure muriate of magnesia, which is alone 

 the cause of the deliquescence of sea salt. 



The salt thus digested in alcohol, and dried, was thrown into 

 toiling water. The solution was not complete. There remained a 



* T'Iip srlt mnsi rmt be exposed to too high a temperature, otherwise a portion 

 of lUe muriate of magnesia \\ ill be decomposed, 



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