Analyses of the Ashes of Plants. 
159 
uhich fact we have satisfied ourselves by passing the gas through 
acetate of lead, which remained unaltered. 
For the purpose of showing that this method gives uniform 
results, we subjoin some experiments made upon white mustard- 
seed, which was chosen as likely to afford a large proportion of 
sulphur ; — 
1000 grains of white mustard-seed burnt in the 
usual way gave . . . . 4'200 sulph. acid. 
1000 grains digested in nitric acid for a suffi- 
cient time to form a pulp, neutralised wilh 
carbonate of soda, and burnt, gave . 30 '038 
1000 grains dissolved in nitric acid, and fresh 
additions of acid made with heat till all 
signs of oxidation had ceased, neutralised 
with carbonate of soda, and burnt, gave . 29 "886 
4th experiment, same as the i)ieceding. . 30'017 „ 
These experiments prove not only that the whole of the 
sulphur in the vegetable substance may be obtained by the 
methods in question, but that it is immaterial to what extent the 
oxidation is carried, so that the plant is eventually burnt in an 
excess of a nitrate. The solution in nitric acid and subsequent 
neutralisation must be regarded merely as a means of procuring 
a thorough incorporation of the nitrate with the vegetable 
matter, a point which is very essential, and is admirably attained 
by the method employed. 
We also instituted some experiments to ascertain how far it 
was possible to dispense altogether with the neutralisation of the 
acid product by carbonate of soda previous to burning. For this 
purpose white mustard-seed was digested in a flask with strong 
nitric acid, a slight heat being applied. Frequent additions of 
the acid were made until the action had comparatively ceased ; 
the acid liquid was then boiled until the evolution of red vapours 
had entirely discontinued ; the liquid was diluted and nitrate of 
barytes added. After standing for some hours the precipitate 
was collected and burnt ; after being weighed it was digested in 
hydrochloric acid, to dissolve some carbonate of barytes due to 
organic salts of this base, and the pure sulphate again collected, 
burnt, and weighed. 
The following results were obtained by this method : — 
1000 grains of white mustard-seed perfectly 
oxidated by nitric acid gave . . 29" 844 of sulph. acid. 
A second experiment, conducted in the same 
way precisely, gave ou lOOU grains . 29*726 of sulph. acid. 
It was desirable to ascertain whether a less amount of oxidation 
