198 J. P. Cooke, Jr., on Lecture Experiments. 
higher boiling point, but the results with amylic alcohol are 
sufficiently accurate for a lecture experiment.* 
Ammonia.—The points to be illustrated in the case of ammo- 
nia are indicated by the equation | HH H+! N || H,N ; 
be found, when the tube cools, that just one-third of the original 
volume is left and it can easily be shown that the residual 
a result, which is sufficient! 
e can obtain with free steam y near the, 
theory for all purposes of illustration, only it is then important that both UN 
vapor uld be 
: measured under a pressure 
poraipadioy serine that of the atmosphere. For this a long eudiometet 
Isis acs pied and before each measurement the evel of the mercury shout 
pe pilusted so that it shall stand in the open tube from 10 to 15 inches lower te 
inthe eudiometer. Of course the difference of level must be the same at » 
