364 J. C. Draper on a new Aspirator. 
It appears that the proportional amount of cerium, in all the 
compounds discussed, varies, within certain limits according to 
the mode of preparation: which is well shown by a comparison 
of the results X, XI, XIL This is as we might expect in com- 
pounds, the nature of which precludes the possibility of purifi- 
cation, either by recrystallization or by thorough washing. 
The roseo-ceric¢ salt appears to contain some admixture of the 
cerous salt. 
The sulphuric acid found is no doubt a little low, as the 
filtrate, after standing a week or more, deposited a slight addi- 
tonal precipitate of baric sulphate to the amount of -05 per 
cent. 
The variations are, it seems to me, not so great as to cast 
doubt upon the correctness of the formulas deduced. 
In conclusion, my best thanks are due to my kind teacher 
and friend, Dr. Wolcott Gibbs, to whom I am indebted for 
many and valuable suggestions, and also for the material use 
in this investigation. 
Lawrence Scientific School, Cambridge, Jan. 15, 1870. 
Art. XXXIX.—On a new Aspirator ; by Joun 0. DRAPER. 
I sEND herewith a description of an apparatus that answers 
irably as an aspirator when it is desired to submit a large 
amount of atmospheric air to examination. 
t consists of a F 
tin boiler (a) for 
h 
one inch in diame- 
ter also drawn : 
| ee hs jet as at 
_ (@) im the figure. : 
_ The two tubes form an ent somewhat like an ordi- 
Hy oxy-hydrogen blow-pipe ‘Through the cork (@) a thin 
