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



weight) of urine. I may observe^ on mixing the urine with the 

 charcoal a veiy strong odour of ammonia was immediately dis- 

 engaged, and the continued evolution of ammonia from the mix- 

 ture for several days was readily detected by moistened turmeric 

 paper ; whereas in the case of the peat, no odour of ammonia was 

 perceptible on making the mixture, nor could the disengagement 

 of the slightest portion of it from the mixture be detected by 

 means of turmeric paper when examined from day to day. 



Having previously determined by experiment how much am- 

 monia was contained in a given quantity of the ammoniacal 

 lu'ine ; after the mixtures had been exposed to the air for four 

 days, I divided each into two equal parts, and ascertained how 

 much ammonia was present in one part of each, containing three 

 fluid drachms of the urine. 



The following are the quantities of ammonia furnished by the 

 same amount of the urine alone, and when mixed with peat and 

 peat-charcoal, and treated in the manner described. 



Amount of Ammonia in 3 drachms by measure. 



In the urine alone .... 0*947 part of a grain, 

 do. with peat-charcoal 0'333 



Loss therefore . 0"714 ... 



do. with peat . . . 1*105 ... 



These results show, that when the urine was mixed with peat- 

 charcoal and exposed to the air for only four days, it lost 0*714 

 part of a grain of ammonia, which is more than three-fourths of 

 the entire quantity contained in the urine ; whereas in the case 

 of the peat, instead of there being any loss of ammonia, there 

 was a slight excess over that existing in the urine alone, which 

 is easily explained by the fact that peat itself always contains a 

 minute quantity of ammonia. 



In these experiments, the quantities of ammonia were ascer- 

 tained by boiling the urine and the mixtures for some time in a 

 retort with a strong solution of caustic potash, and collecting 

 the evolved ammonia in a given quantity of diluted sulphuric 

 acid of known strength, and determining its amount by Peli- 

 got's method, which is one much used by chemists on account 

 of its accuracy and expedition. 



I made also the following experiments, which confirm the 

 results of those just noticed. Having weighed 300 grains of 

 peat and of peat-charcoal, I carefully mixed each with half an 

 ounce by measure of the same urine as that employed in the 

 former exj^eriments, and putting each mixture on a small saucer 

 placed it in a large plate holding some mercury, and having 

 arranged a small tripod supporting an evaporating dish contain- 



