in &ome Artificial Manures. Ill 



looked perfectly green and healthy. On examining it for arsenic, 

 I obtained the most distinct indications of the presence of that 

 substance^ though only a very small amount of cabbage, viz. 113 

 grains, were used in the experiment. This result was therefore 

 perfectly conclusive as to the power possessed by some plants, at 

 least, of taking up arsenic from manures containing that sub- 

 stance. As in this experiment I was aware that I had placed 

 the plant in a most favourable condition for absorbing the poison, 

 and that a larger proportion of superphosphate had been em- 

 ployed than was used in practice, my last experiments were to 

 ascertain if the presence of arsenic could be detected in our crops 

 grown with superphosphate in the ordinaiy way. 



I procured for this purpose some Swedish turnips which had 

 been grown with superphosphate, and having most carefully 

 washed each turnip to remove every particle of adhering clay, I 

 cut up in small pieces 2 lbs. weight of one of the turnips, and 

 boiled them in a large glass flask for about three houre with 36 

 fluid ounces of distilled water, to which I had added 3 ounces of 

 hydrochloric acid (spec. grav. 1'14), placing in the mixture a 

 hundred grains of perfectly clean and bright turnings of metallic 

 copper. After removing the copper turnings and washing them 

 well with water to separate the vegetable matter, and then boil- 

 ing them for a few moments in a mixture of spirit and ether to 

 remove any fatty matter which might have been deposited on the 

 metallic copper, and finally, after the spirit and ether had been 

 poured ofi", washing well with distilled water, the copper was 

 found to have acquired the characteristic steel-grey appearance 

 produced by the presence of arsenic under such circumstances. 



The copper turnings were then carefully dried, and afterwards 

 heated strongly in a glass tube closed at one end, when a very 

 perceptible white sublimate was produced, which, on being dis- 

 solved in hot distilled watei-, and this solution added to a Marsh's 

 apparatus in operation (the hydrogen flame, which before the 

 addition of the solution did not give the slightest indication of 

 a metallic stain on a cool piece of white porcelain being placed 

 over it), produced immediately the characteristic stains of me- 

 tallic arsenic in a most striking manner, proving beyond all 

 doubt that the matter deposited on the copper was metallic 

 arsenic, and the sublimate arsenious acid, formed during the 

 heating of the metal. 



This experiment was repeated with the same results, using 

 2| lbs. weight of turnip taken from another of the turnips, it 

 being previously peeled. I may observe that in these, as well as 

 in the foregoing experiments, 1 was most careful that no source 

 of fallacy might arise from the arsenic being derived from the 

 reagents employed, which were previously ascertained to be free 



