183 Mr. A. B. Northcote on the Function of Salt 



had occuiTed was considered to be clearly proved. Water was 

 then added in quantity just sufficient to moisten the salt, and 

 upon the re-insertion of the test-paper, a diminished blueing 

 showed that the ammonia was being absorbed* ; water was again 

 added, yet in insufficient quantity to dissolve the whole of the 

 salt, and the action upon the litmus was gone. In this way, by 

 alternating the addition of the ammonia and the solution of the 

 salt, the presence of the ammonia might be rendered more or less 

 distinct, or unrecognizable. The reality of the absorption was 

 thus rendered undeniable ; and it was equally evident that the so- 

 luble portion of the salt contained the absorbing agents, since the 

 disappearance of the ammonia bore a direct proportion to the com- 

 pleteness of their solution. It then became a question as to which 

 of the constituents of the soluble portion this agency was due. 



Now the chloride of sodium being the largest ingredient, it 

 was desirable at once to ascertain the part which it played in the 

 matter : a saturated solution of the pure substance was therefore 

 prepared, measured quantities of it taken, placed in bottles, and 

 shaken with successive portions of carbonate of ammonia solu- 

 tion until a decidedly blue tinge was produced in the litmus- 

 paper, which, for the purpose of having a standard test, was left 

 enclosed in the atmosphere within the bottle for the space of five 

 minutes. As the amount of ammonia added approached the 

 maximum, its absorption became correspondingly slower, and it 

 was necessary to leave it in contact with the salt solution for 

 periods of from one to twelve hours; a point was, however, 

 always reached at which a certain tinge of colour was communi- 

 cated to the paper, the intensity of which was not lessened if the 

 test was applied again after a lapse of several days. 



The following are the • results which I have obtained in expe- 

 rimenting with a saturated solution of pure chloride of sodium 

 in the above manner : — 



These numbers require a slight correction to make them abso- 

 lutely true expressions for the absorbing power of chloride of 



* With regard to the delicacy of the litmus-paper here employed, I may 

 state that a quantity of the ammonia sohition containing "04 of a grain of 

 NH^O, being placed in an empty bottle, the paper was intensely blued 

 Almost immediately after its insertion. 



