INCOMPATIBILITY 47 



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, hypophosphites, ammonium chloride, tannic acid or other 

 organic substance, will explode violently. 



EuLE 3. Silver nitrate is incompatible with organic material 

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

 or hydrochloric acid it forms insoluble silver chloride. 



EuLE 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. 



EuLE 5. Corrosive mercuric chloride (corrosive sublimate) is 

 incompatible with iodides, many metallic salts, alkaloidal salts, tan- 

 nic acid, lime water, and albumen. 



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

 curic oxide, and forms " yellow w^ash," employed as an application 

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

 tate is red oxychloride. 



With soap, as on the surgeon's 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 the 

 biniodide. 



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

 the drug is swallowed. 



EuiE 6. Lead acetate decomposes alum and other sulphates 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 should be filtered out. The precipitate with 

 the iodide is lead iodide of a brilliant yellow. 



EuLE 1. Ferric salts — (a) Make " ink " with tannic acid; (b) 

 make blue to reddish or purple colors with compounds of the phenol 

 group, such as phenol, resorcin, salicylates, etc. ; (c) make red color 

 with acetates ; and (d) form a dirty brown precipitate with alkalies 

 or alkaline salts. 



EuLE 8. Tannic acid is incompatible with alkaloidal salts, dry 

 potassium chlorate (explodes), metallic salts, gelatin, and albumen. 

 With ferric salts it makes " ink." Por salts of alkaloids and anti- 

 mony it is the local antidote. 



it occurs in many vegetable drugs, and preparations of these may 

 not only precipitate alkaloidal salts, but may change the gelatin coat- 



