354 MANUAL OF EQUINE MEDICINE. 



Antimoniuretted hydrogen, however, does not burn with 

 the odour of arseniuretted hydrogen. 



The antimonial deposit is sooty, and has not a metallic 

 lustre, and is darker than that of arsenic, which is of a 

 browner hue. The arsenical deposit is, moreover, readily 

 dissolved by a solution of chloride of lime (bleaching 

 powder), whilst that of antimony is not affected. 



To the stain may be added a few drops of nitric acid, 

 which will be found to dissolve the arsenic. 



If this be now allowed to evaporate, and the acid be 

 neutralized, a few drops of nitrate of silver will give a 

 brick-red precipitate of arsenate of silver. 



Marsh's test may be carried out in the following way : 



A flask is furnished with a cork, through which pass a 

 funnel and a long test-tube drawn to a point, and the 

 funnel is made to reach almost to the bottom. 



Several pieces of pure metallic zinc are now introduced, 

 and then some dilute sulphuric acid is passed through the 

 funnel. 



In this way hydrogen is produced, and escapes by the 

 test-tube. When all the air has been expelled the gas 

 should be ignited as it escapes, and a piece of cool porcelain 

 held over the flame. 



If there be no deposit, it is plain that neither the zinc 

 nor the sulphuric acid contains arsenic. 



A portion of the suspected fluid is next introduced into 

 the flask by the funnel, and the escaping gas again tested. 



Should a stain, giving the characters alluded to above, 

 be produced, the fluid contains arsenic in some form or other. 



lleinscKs Test. — The liquid suspected is boiled with one- 

 sixth to one-eighth of its bulk of pure hydrochloric acid, 

 and a bright slip of metallic copper is introduced. 



If arsenic be present, the copper will be coated with it 

 in the form of an iron-grey deposit. 



