176 Mr. E. W. Davy on the comparative Value of Peat 



it was found that the mixture with peat-charcoal was still evol- 

 ving ammonia. 



These experiments show that peat-charcoal (contrary to the 

 many statements which have been made by its advocates) has 

 very little power of absorbing and retaining the ammonia of ex- 

 crementitious matter when mixed with it ; whereas peat possesses 

 this valuable property in an eminent degree, and absorbs and 

 retains it in a most striking manner, which would appear to be 

 owing (at least in part) to peat containing some substance which 

 acts the part of an acid in neutralizing and fixing the ammonia of 

 the volatile carbonate ; for I found that when peat in certain 

 proportions was mixed with urine which was highly alkaline 

 (fi'om the quantity of carbonate of ammonia it contained), and 

 the mixture filtered after a short time, that the filtrate, though 

 it contained ammonia, was quite neutral to test-papers, showing 

 evidently that the ammonia of the carbonate had combined with 

 some other acid to form a neutral salt. The evolution of am- 

 monia in the case of peat-charcoal seems to arise from two causes, 

 namely, its inability to retain the volatile cai'bonate of ammonia 

 existing in decomposing animal matter, and the property I have 

 observed it to possess of decomposing to a certain extent the 

 fixed salts of ammonia, as, for example, the sulphate, phosphate, 

 muriate, and urate which may be present in such mattei", and 

 converting them also into the volatile carbonate which is readily 

 evolved. This latter property would seem to depend on the 

 alkaline and earthy carbonates formed during the process of 

 chai'ring ; for when the charcoal was boiled for some time in 

 diluted muriatic acid, and well washed with distilled water so as 

 to remove as much as possible those salts, and again dried at a 

 red heat, the power it possessed of decomposing the fixed salts 

 of ammonia, though not completely removed, was, however, 

 greatly diminished, which clearly shows its connexion with those 

 substances. Peat, on the other hand, does not possess this pro- 

 perty in the slightest degree. These facts prove the great su- 

 periority of peat over peat-charcoal for agricultural purposes as 

 regards the important substance ammonia; for by the use of 

 peat, the ammonia is retained more or less completely in the 

 manure to exercise its fertilizing action on vegetation, whereas 

 the peat-charcoal suflfers it to be in greater part dissipated and 

 lost. 



The foregoing results and statements, as regards peat-charcoal, 

 are contrary to what might have been anticipated from the ex- 

 periments of De Saussure and other chemists, who have shown 

 that charcoal possesses the power of absorbing difi^rent gaseous 

 substances, and particularly ammoniacal gas, in large propor- 

 tion ; but the circumstances under which they conducted their 



