Composition of Waters of Land-Drainage and of Rain. 159 



The foregoing are probably sufficient illustrations of the 

 accuracy of this process. They are fair instances of the actual 

 results, and wherever greater deviations are found to occur, 

 which is very seldom the case, the cause is generally discernible 

 during the process of analysis, and may be avoided by due care. 



It is only further necessary to remark, that the possible sources 

 of error in this method have been carefully looked into. The 

 most probable would be the production of nitric acid by the 

 action of the permanganate of potash, either on ammonia or 

 nitrogenous organic matter in the waters. I have satisfied myself, 

 by direct experiments, that in neither case does such production 

 of nitric acid occur. 



Determination- of Ammonia. 



The accompanying woodcut will probably be understood 

 without much explanation. Into the bottle a, which has a 

 capacity of about 1 gallon (70,000 grains), a quart of the water to 

 be examined is introduced, together with a small quantity of 

 lime, and a quantity of recently fused common salt, the object 

 of which last will be immediately explained. This vessel is con- 

 nected with the bottle d by glass tubes c of about | of an inch 

 external diameter. 



The vessel c? is a bottle with two necks, into which the glass 

 tubes are ground ; into this vessel is introduced a solution of 

 bisulphate of potash, for the purpose of collecting the ammonia 

 brought over by distillation from the liquid in a. 



The tube c connecting these vessels cannot obviously form a 

 stopper, and at the same time continue of any length into the 

 bottle d, but a smaller tube is by means of an India-rubber joint 

 connected with it, so as to dip into the liquid in the vessel d. 

 The same is true of the tube h, which connects d with e, but 

 which stops short at about two-thirds of its depth. 



The vessel e is surrounded by cold Avater in an outer vessel y. 



At r/ the apparatus is connected with the pump at the point li 

 in the nitric acid apparatus. As these two operations have, in 

 the case of waters, to be carried on at the same time, it is con- 

 venient to have the respective apparatus attached to the same 

 pump. 



Such being the arrangement, heat is applied to the water bath h, 

 and a vacuum is created tliroughout the apparatus by the pump. 

 When the liquid in a commences to boil, a trilling condensation 

 at first occurs in the tube c and the vessel d, but these soon come 

 to have a temperature equal or nearly equal to the liquid in a, 

 and from tluittime the bubbles of vapour pass througli the liquid 

 in d, just as would a fixed gas, and are finally condensed in c, so 



