17 



ide (chromic acid), potassium permanganate, and potassium chlor- 

 ate are decomposed by organic matter. Potassium permanganate 

 in solution turns brown ; dry potassium permanganate or chromic 

 acid may take fire or explode. Potassium chlorate, when rubbed 

 with sulphur, hypophosp'hites, ammonium chloride, tannic acid or 

 other organic substance, will explode violently. 



Rule 3. Silver nitrate is incompatible with organic material 

 and turns to black oxide or black metallic silver. With chlorides 

 or hydrochloric acid i't forms insoluble silver cbloride. 



Rule 4. (Mild mercurous chloride) calomel is incompatible 

 with sodium carbonate and lime water. With the latter it makes 

 a black precipitate of mercurous hydroxide, and forms "black 

 wash", sometimes employed as an application to venereal sores. 



Calomel is insoluble in water or alcohol, comparatively inert 

 chemically, and bland to tissues. 



Rule 5. Corrosive mercuric chloride (corrosive sublimate) is 

 incompatible with iodides, many metallic salts, alkaloidal salts, 

 tannic acid, lime water, and albumen. 



With excess of lime water it forms a yellow precipitate of mer- 

 curic oxide, and forms "yellow wash", employed as an applica- 

 tion to venereal sores. When the mercury salt is in excess, the 

 precipitate is red oxychloride. 



With soap, as on the surgeons hands, its antiseptic power is 

 destroyed. 



With potassium iodide it forms mercuric biniodide. The iodide 

 is of a brilliant scarlet color and dissolves in excess of potassium 

 iodide. These two salts are often prescribed together to form bin- 

 iodide. 



In albumen, as in white of egg or milk, we have the antidote 

 when the drug is swallowed. 



Rule 6." Lead acetate decomposes alum and other sulpliates 

 and the iodides, and tends to precipitate many organic substances, 

 e. g., glucosides, from their solutions. 



The admixture with alum makes Burow's solution. The pre- 

 cipitate of lead sulphate s'hould be filtered out. The precipitate 

 with the iodide is lead iodide of a brilliant yellow. 



