Chemical Notices :—Preparation of solid Carbonic Acid, 495 
peste) aciqe phe wig | ‘eal 
Bie tlh geo Dk ». OR gh DBrytrer OH 
er. Ye ie te 
ed Ba tO eae 
eee a 2, ORR 
Hence if 1, 2, 3, 4 are the centres of spheres radii a, B, y, 8, 
and if O is the centre of a tangent sphere radius 7, we have 
Ol=r+a, O2=r+P, O8=rty, 04=r4+6; 
so that, for any given combination of signs, it would at first 
sight appear that r is determined by a quartic equation; but by 
means of a simple transformation (indicated to me by Prof. Syl- 
vester) it may be shown that the equation for 7 is really a qua- 
dratic one ; morcover, the equation remains unaltered if the signs 
of a, B, y, 6 and of r, are all reversed; and 7? has thus in the 
whole sixteen values. In particular, if «, 8, y, 6 are each equal 
0, then r? is determined by a simple equation (r the radius of 
the sphere through the four points) ; and if, moreover, r=O, 
then we have for the relation between the distances of the four 
points, the foregoing equation 0=0., 
2 Stone Buildings, W.C., 
March 25, 1861. 
cn A a = pescmmasitainnntnmmntiieniiil 
- 
ana a = —— = = TT 
LXXIII. Chemical Notices from Foreign Journals. 
By i. Arxinson, Ph.D., FCS. 
[Continued from p. 365. | 
M. LOIN and Drion* describe the following method of ob- 
taining solid carbonic acid, merely requiring for its prepa- 
ration apparatus within the ordinary reach of the laboratory. It 
depends on the great cold produced by the evaporation of liquid 
sulphurous acid. Liquid ammonia is placed in a glass vessel, 
and connected with the receiver of an air-pump by a vessel con- 
taining pumice impregnated with sulphuric acid. On exhausting, 
the temperature of the liquid ammonia rapidly sinks, and it com- 
mences to solidify at —81° C.; when the pressure is reduced to 
1 millim., the temperature of the liquid ammonia is —89%5, 
This is sufficient for the liquefaction of carbonic acid under the 
ordinary atmospheric pressure ; for when a current of dry carbonie 
* Comptes Rendus, April 15, 1861. 
