422 i, Scientific Intelligence. 
with a vacuum m4 have the same temperature and the same quan- 
tity of heat in spite of the dilatation, and if the volume of the vacuum 
is the fraction a of the cubic metre the pressure will again become H. 
Now take again a cubic metre of air at 0° and under a pressure H, and 
let C denote the specific heat under a constant pressure, Give to this 
air the heat p C, permitting it this time to dilate under = pressure which 
it supports, We thus obtain a volume 1-++aat 1° under a pressure 
precisely as in the preceding case in which ening we have only intro- 
duced the quantity of heat pc. But in the first case there was no ex- 
ternal work, while in the second the dilatation a under the pressure H 
their initial and terminal states, they both contain precisely the same 
quantity of heat. We have therefore a right to conclude that the heat 
p(C—c) is becloneoe employed in producing the work a Conse- 
aH 
— By taking the num- 
p(C-¢) 7 
bers H=10334k, p—1'-293, C —0-1686 according to Laplace, and 
e=0-2377 according to Regnault, we find 424 4 kilogranametres for the 
mechanical equivalent of heat.—Comptes anes xxxix, 1131, De- 
cember, 18 Ww. G 
quently the work of the unit of heat is 
5. A new Carbonic Acid Apparatus ; communicated be Arrep M. 
Maver, of Professor Morfit’s Laboratory, University of Maryland.— 
Having lately invented an apparatus, for the es- 
timation of carbonic acid in carbonates, or rather 
made a modification of Will’s and Fresenius’s 
apparatus, I have ae it might be of some 
service to science ; d I therefore ‘ictnd you a 
drawin (half-size) a the dimensions marked. 
The following i is the description of the drawing. 
Ais a flask, at the bottom of which is placed the 
carbonate with a little water. B is a short piece 
sing footn the tube B thr ough the cork of the 
flask. Bis another hole perforating the cork of 
the flask, 
After the carbonate is introduced into the flask 
Ur), the tube (B) is nearly filled with eon 
acid, and being attached to the cork A’ by the 
tube Di is inserted into the fteskst The tube E 
ee brium is restored in B, but the air in A being 
in mah in tee fia pear the acid sleet over eit the sy- 
? ; i The acid 
with t : 
