544 Mil. J. 13. LAWKS, DR. OILBEET, AMJ DR. PUGH "N 



previously covered portions of the slate or stonc-warc lute were then washed with pure 

 distilled water, and the wash-water was added to the condensed or drain-water. In the 

 experiments of 1858 this fluid was analysed separately, but in those of 1857 it was 

 mixed and dried down with the soil. 



The pot, with the soil and plants, was removed to a clean table covered with white 

 paper, the plants measured in all their parts and then cut off at the surface of the soil ; 

 the roots were removed, slightly washed from soil, and observed. The plant, were then 

 put into a small wide-mouthed bottle, generally stem and root together, but sometii 

 they were put into separate bottles. In the experiments of 1857 the contents of the 

 bottles were dried in a water-bath, with a current of air, previously washed tlirough 

 sulphuric acid, passing through the bottle and thence through a solution of a known 

 quantity of pure oxalic acid. But it was found that no appreciable amount of ammonia 

 was thus accumulated. Hence, in 1858, a little oxalic acid (in solution) was added to 

 the vegetable matter, and the whole dried in the water-bath without the above pre- 

 caution. 



When dry, the vegetable matter was cut small by means of a pair of clean long 

 scissors, reaching to the bottom of the bottle. In this way the substance was reduced 

 to a considerable degree of fineness, and it was still further ground up in the mortar 

 when mixed with soda-lime for analysis. When duplicate analyses were to be made, the 

 matter was carefully divided so as to ensure equal proportions of stem, fine leafy matter, 

 &c., in each half. Hence, if both analyses were successfully conducted, the results were 

 mutually confirmatory ; or if one portion were lost, the other still represented a propor- 

 tionate amount of the whole material. 



The soil was removed from the pot to a porcelain dish, and a sufficient amount of a 

 solution of oxalic acid added to keep it acid. The mixture was then heated on a sand- 

 bath (stirring constantly) until most of the water was expelled, more fully dried in a 

 water-bath, and then preserved in well-corked bottles for analysis. The pots were pounded 

 up; those of 1857 being preserved and analysed separately, and those of 1858 mixed 

 with the soil before it was dried with oxalic acid. The pieces of flint at the bottom of 

 the pot were also pounded and mixed with the soil. 



For analysis, 150 to 200 grammes of the soil, pot, or mixture, were mixed with about 

 half the volume of soda-lime, the whole put into a large combustion- tube, some soda- 

 lime put in advance of the mixture, and then asbestos, as usual. The combustions 

 were made in charcoal furnaces, and the ammonia collected in titrated sulphuric acid, 

 of which the strength, and the amounts employed, are described at pp. 545, 546. When 

 very small quantities of nitrogen were involved, the ammonia from two or three tubes of 

 substance was sometimes collected in the same quantity of acid, so as to diminish the 

 error of titration. It was found, however, to be better to use very small quantities of 

 acid, and to estimate the product of each combustion separately ; for, by the former 

 method, if any accident occurred in the second or third combustion, it involved the loss 

 of the determination of the products previously collected. 



