498 MR. J. B. LAWES, DR. GILBERT, AND DR. PUGH ON 
A number of experiments according to the first of these methods has been made by 
Reiser. He submitted nitrogenous animal and vegetable substances to decomposition 
under an enclosing vessel in ordinary air, into which he passed oxygen as that of the 
air was consumed. His result was, that the amount of Nitrogen in the air was gradually 
increased. He does not appear, however, to have completed the inquiries on this sub- 
ject which he proposed to undertake. 
The second method has been followed by M.G. Vitis. The conclusion he arrived at 
was, that in the decomposition of several nitrogenous vegetable substances, about one- 
third of their total Nitrogen was evolved in the free state. 
The losses of Nitrogen which M. Bousstneavtt’s experiments on the question of the 
assimilation of free Nitrogen by plants indicated, when he used nitrogenous organic 
matter as manure, rendered it desirable to investigate the subject in its bearings upon 
the conditions provided in our own experiments on that question. The following plan 
was adopted :— 
A given weight of nitrogenous organic matter, the percentage of Nitrogen in which 
had been previously determined, was mixed with burnt soil, or pumice, prepared as for 
the experiments on the assimilation of Nitrogen by plants (p. 471), and put into a bottle 
of about 360 cub. centims. capacity, as shown at B, fig. 8, Plate XII. A proper quantity 
of water was added; and then the bottle was closed with a cork, through which were 
tightly fitted two bent glass tubes, which passed externally in opposite directions. One 
of these tubes was connected with an eight-bulbed apparatus A, containing sulphuric 
acid, for the purpose of washing air drawn through it into the rest of the apparatus. 
The other tube, passing from B in the opposite direction, was connected with a similar 
eight-bulbed apparatus C, containing a solution of oxalic acid. From this again passed 
a tube extending, through a cork, to the bottom of a second bottle D (similar to B), 
which contained some sulphuric acid. Through the cork of the bottle D another tube 
E also passed, but it did not dip into the sulphuric acid. It is obvious that, on drawing 
the air from D by means of the tube E, a current of air would pass inwards through 
the sulphuric acid in A, into the bottle B, then through the oxalic acid in C, and so on. 
In this way, the air of the vessel B, containing the decomposing organic matter, could 
be renewed at pleasure by fresh air, washed free from ammonia. At the same time, any 
ammonia evolved from the decomposing organic matter was drawn into the eight-bulbed 
apparatus C, and there absorbed by the oxalic acid. At the termination of the experi- 
ment, the combined Nitrogen remaining in B, and that retained in the form of ammonia 
in the oxalic acid in C, were determined. The difference between the total amount of 
combined Nitrogen so found in the products and that originally contained in the organic 
substance submitted to decomposition, is taken to represent the amount of nitrogen 
given off, in the free state, during the process. 
