66 PROCEEDINGS OF THE AMERICAN ACADEMY 



tioned that Bi'unner* has distinctly called attention to the extreme 

 difficulty of completely absorbing carbonic acid from the air. Brunner 

 could accomplish this neither by means of a solution of baryta, nor 

 by a mixed solution of chloride of barium and caustic ammonia,t by 

 bits of sponge moistened with baryta or lime-water, nor even by frag- 

 ments of caustic potash, or asbestos moistened with a solution of 

 potash ; he finally chose slightly moistened hydrate of lime, as the 

 best absorbent, and maintains that his method of determining carbonic 

 acid in the air, by this means, is sufficiently accui'ate for all ordinary 

 cases. J 



Professor G. P. Bond presented a memoir on the Light of 

 the Moon and of the Planet Jupiter, containing the results of 

 photographic and optical experiments upon the light of these 

 two bodies. 



The rays from Jupiter have been found to possess a remarkable 

 degree of chemical energy compared with those reflected from ordinary 

 opaque substances on the earth, and from the Moon ; a similar excess 



* PoggendorflF's Ann. der Phys. u. Ch., 1832, XXIV. 571. 



t Having had repeated opportunities of observing the great difficulty — not to 

 say impossibility — of absorbing carbonic acid from mixed gases, especially if 

 these contain so much as one or two per cent of it, by means of these and similar 

 liquids, I am glad^to bear witness to the entire accuracy of this much-neglected 

 statement. — f. h. s. 



J It is a curious fact, M'hich not only corroborates Brunncr's observation, but 

 also suggests a more extended use in the laboratory of his favorite absorbent, that 

 manufacturers of coal-gas find in practice, that carbonic acid, when not present in 

 very abnormal quantity, may be readily removed from the impure gas by passing 

 the latter through several layers of dry hydrate of lime, spread in fine powder upon 

 perforated iron grates or upon shelves of basket-work ("dry-lime purification"); 

 while it is practically impossible to absorb all the carbonic acid from similar gas by 

 the wet system, in which the impure gas is forced through milk of lime contained 

 and agitated in several successive purifiers. Yet with the other chief impurity of 

 coal-gas, sulphuretted hydrogen, the reverse of this is the case, for by means of the 

 wet-lime purification, this substance can, in ordinary cases, be very readily and 

 completely removed with an expenditure of but little lime, while with the dry 

 purification this result is far less easily attained. Moreover, this non-absorption 

 of carbonic acid in the wet-lime purifiers cannot be due to any interference 

 caused by the sulphuretted hydrogen, for it is just as difficult to absorb all the 

 carbonic acid from rosin-gas, which contains no sulphuretted hydrogen, as it is to 

 absorb that in the gas prepared from coal. 



