30 DECOMPOSITIONS BY BINARY ARRANGKMKNTS. 



barrier. The condition under which we obtain the mechanical result will, by being 

 duly varied, also furnish chemical results, an investigation of which forms our next object. 



90. CHEMICAL DECOMPOSITION; and, first, by BINARY ARRANGEMENTS. A solitary ar- 

 rangement of any kind, whether it be of a simple or of a compound nature, has no pow- 

 er of change in itself; but it is conceivable that one of the latter kind compound on 

 forming part of a binary arrangement, may be differently affected ; as an illustration, let 

 us take atmospheric air and water, appropriately situated, to form such an arrangement 

 (63). In this case, were the nitrogen and oxygen equally absorbable by the liquid, no 

 remarkable result would ensue ; but such is not the fact ; the oxygen gas passes much 

 more quickly into the water than the niti'ogen, and decomposition takes place, an ex- 

 cess of oxygen being in the liquid, and an excess of nitrogen being left. We should, 

 therefore, expect that rain, and dew, and springs, and rivers, which have been exposed 

 in a very divided state to the air, ought to contain a gas richer in oxygen than that of 

 the atmosphere ; and such, in fact, is the case, the atmosphere containing one volume 

 of oxygen and four of nitrogen, the gas of water containing one of oxygen and two of 

 nitrogen, as we shall shortly find. 



91. Instead of a gas and a liquid to form these binary arrangements, a solid and a 

 gas may be used. Into 500 measures of atmospheric air, a piece of charcoal, that had 

 been made red hot and quenched under mercury, was placed. The volume of the air 

 experienced a rapid diminution, and after the absorption had gone on for several hours, 

 there remained 205 measures, 100 of which contained only eight of oxygen. The 

 charcoal was now introduced into water over mercury, and commenced very actively 

 evolving gas, which contained only 3-75 per cent, of oxygen, and the last portions of it 

 that were given off, only 2-8. Solution of lime was not capable of detecting the pres- 

 ence of carbonic acid in the water. 



92. In the place of charcoal, other porous solids might be substituted ; into a jar, #, 

 which contained atmospheric air, there was introduced a piece of red-hot pumice stone; 

 into b, a piece of clay that had been made red hot ; and into c, a piece of charcoal 

 quenched under water. Absorption took place in them all, and in a quarter of an hour 

 a was found to contain 19 per cent, of oxygen, shortly after &was found to contain 19 

 per cent, of oxygen, and c, in half an hour, only 18 per cent. Also, in five hours, c only 

 contained 17-25 of oxygen, and in seven days, only seven per cent.; but, at the same 

 time, a and b contained 14-50 per cent. Four days after, c contained only five per cent. 



93. By long boiling, I extricated all the air possible by such a process, from a quan- 

 tity of water, and pouring it into a glass cup, left it exposed to the atmosphere for some 

 days ; at the end of that period the water was again boiled in a close vessel, and the 

 gaseous matter it had absorbed submitted to analysis. After the carbonic acid had been 

 carefully washed off, its amount being about 29 per cent., it was found that the residue 

 contained 32 1 per cent, of oxygen gas. It is a singular fact, that an aqueous mass, in 

 thus decomposing atmospheric air, appears to follow a very simple law; pure spring water 

 and distilled water, after a competent exposure to the atmosphere, are found to contain 

 a gas whose elements are not in the proportion of one to four, as in the case with the 

 atmosphere, but in the proportion of one to two. In several analyses of the air, extrica- 



