to the Earthy Constituents presented to their Absorbing Surfaces. 255 



notes, I will in the first instance refer to one made in 1827, in which grasses 

 and trefoils of various kinds, which had been watered from time to time with 

 a solution of nitrate of strontian, were found on examination to possess no 

 trace of this earth *. 



In the above instance, however, as the plants had grown in common garden 

 mould, all that could be inferred was, that when lime and strontian are both 

 presented in a state of solution to their roots, they select the former, and reject 

 the latter. 



In 1829, the seeds of various plants, such as the garden radish {Raphanus 

 sativus), the cabbage (Brassica oleracea), the garden bean {Ficia Faba), hemp 

 {Cannabis safiva), &c., were sown in soils containing various proportions of 

 sulphate of strontian, with or without manure, and amongst the rest, one in 

 which no other ingredient, except this earth, was present in any quantity. 

 The plants grew up, and when they had arrived at maturity, were collected, 

 burnt, and their ashes examined. No strontian, however, could be detected 

 in any one of them, not even in that where the matrix consisted almost wholly 

 of the earth in question. 



In 1831, the experiments were conducted with rather more attention to 



* I will state, for the satisfaction of chemists, the method I pursued to determine whether strontian 

 was or was not present. 



After washing off the alkaline salts from the ashes by lixiviation in warm distilled water, I digested 

 the residuum in diluted nitric acid. This first acted upon the earthy carbonate, and afterwards upon 

 the earthy phosphate. The solution in nitric acid consequently contained both. Ilie phosphate being 

 thrown down by ammonia, the nitrate remaining in solution, rendered exactly neutral, was evaporated 

 by a heat never exceeding 212°, in a flask, and when dried, the mouth of the vessel was closely stopped 

 by a cork. When cold, alcohol of the sp. gr. of '815 was poured upon it, which would dissolve all 

 the nitrate of lime. If there was no undissolved residuum, the absence of strontian from this portion 

 of the ashes might be fairly inferred. If there was any, I generally digested it with a solution of car- 

 bonate of soda, and after filtering, heated the earthy residuum in a covered capsule, so as to expel the 

 carbonic acid. A small quantity of distilled water would then generally dissolve the whole ; and if 

 the addition of a drop or two of sulphuric acid to this solution did not render it turbid, I felt myself 

 justified in concluding that no strontian was present. The precipitate, if any, was concluded to be 

 sulphate of strontian. 



A similar procedure was adopted with reference to the earthy phosphate, and likewise to that jjor- 

 tion of the ashes which remained undissolved by the nitric acid upon its first application. In botli 

 cases, digestion with an alkaline carbonate reduced the earthy matter to a fit condition to be acted 

 upon by nitric acid, and the subsequent steps pursued to determine the presence of strontian in it 

 corresponded with those already detailed. 



