68 VETERINAEY TOXICOLOGY 



Treatment. — Soluble sulphates, such as those of sodium 

 or magnesiuin, are indicated as chemical antidotes, operating 

 by the formation of the insoluble barium sulphate. Re- 

 moval of the cause by purgatives, emetics, and the pump 

 is required. When given intravenously the prognosis is 

 grave. The depressant action is combated by stimulant 

 and excitant drugs, and oxygen has been recommended. 



Chemical Diagnosis. — Since the sulphate of barium is 

 so very insoluble in acids, the salts of this metal are con- 

 verted into the sulphate and lost in the residue of the 

 nitric acid extraction process used for lead. Special search 

 may be made for barium in a hydrochloric acid or nitric 

 acid residue, the former being preferable, as nitric acid 

 might oxidise barium sulphide to sulphate. By boiling 

 the clear extract in hydrochloric acid with calcium sulphate 

 solution, or dilute sulphuric acid, a white precipitate of the 

 sulphate is got. This is collected and fused in a crucible 

 with a mixture of potassium and sodium carbonates. After 

 washing with water, the residue of barium carbonate is 

 dissolved in acetic acid and special tests applied, viz., 

 formation of insoluble barium sulphate with calcium sul- 

 phate, or sulphuric acid solution ; formation of yellow 

 insoluble barium chromate by addition of potassium 

 chromate. To distinguish from lead, the acetic acid solution 

 is shown to give no black sulphide with sulphuretted hydro- 

 gen and no insoluble iodide with potassium iodide. 



CHROMIUM. 



Forms and Occuprence. — Chromic acid is a powerful 

 corrosive which destroys all tissues. The corrosive effect 

 is shared to a less extent by the orange potassium bichro- 

 mate, and still less by the yellow potassium chromate. The 

 green basic, chromium oxide, is stated to be harmless. 

 Several cases of poisoning by potassium bichromate, which 

 is widely used in the arts, have been recorded in man, and 

 the salt appears to operate occasionalljj^ less by reason of its 



