504 Boussingault on the Composition of the Water of the Dead Bea. 



corresponding to 500 hectolitres per hectare. But the same 

 substance which had entered into fermentation gave in six hours 

 results corresponding to the enormous quantity of 8800 hecto- 

 htres per hectare in the twenty-four hours, or 77,440 gallons 

 per acre. 



Experiments were made also with various organic substances : 

 sugar as well as wood-charcoal moistened gave no carbonic acid, 

 and guano only a small quantity; linseed-meal produced a con- 

 siderable quantity of carbonic acid. 



It is generally assumed that the carbonic acid absorbed by 

 plants is almost entirely derived from the respiration of animals, 

 and a balance between these two kingdoms has been established 

 M'hich must be considered too absolute if we take into account 

 the enormous quantity of carbonic acid assimilated every year by 

 plants. These experiments show, Corenwinder thinks, that it is 

 more conformable to nature to ascribe to the carbonic acid pro- 

 duced at the surface of the soil the greater part of the alimenta- 

 tion of vegetables. 



Boussingault* has examined the water of the Dead Sea. His 

 principal object was to ascertain if nitrates were contained in it, 

 as these had not been found by Gmelin. Boussingault thinks 

 that nitrates have frequently been stated to be pi*esent where they 

 did not exist, owing to the imperfection of the methods, or the im- 

 purity of the materials used in their detection. He had used the 

 method with gold, but he found that it was not to be depended 

 upon, owing to the impurity of the hydrochloric acid, which fre- 

 quently contains nitrous compounds. By boiling the acid so as 

 to drive off about a fourth, they are got rid of. The method used 

 by Boussingault, consisted in adding to the water to be tested 

 about an equal bulk of pure hydrochloric acid, colouring the 

 mixture with a few drops of water rendered blue by tincture of 

 indigo, and then boiling. If nitrates be present, the liquid be- 

 comes decolorized. This test is so sensitive that Boussingault 

 could detect the presence of nitrates even in so small a quantity 

 as O'OOOOOSl grm. in a cubic centimetre of water; and as this 

 quantity may be the residue of the concentration of a litre, the 

 test may be taken to be infinitely delicate. In examining for 

 nitrates in sea-water or saline solutions, it is desirable to add an 

 excess of hydrochloric acid. 



The composition of the water Boussingault found to be as fol- 

 lows; the adjoined analysis by Moldenhauer is the most recent, 

 with the exception of Boussiugault's ; that by Gmelin was made 

 thirty years ago : — 



* Annates de Chimie et de Physique, October 1856. 



