18 



Rule 7. 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. 



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

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

 With ferric salt's it makes "ink". For 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 

 coating of a pill or gelatin capsule to a tough leathery insoluble sub- 

 stance. Alcohol may prevent the precipitation of alkaloidal salts 

 by tannic acid, as in tinctures. 



Rule 9. Chloral hydrate decomposes to chloroform ixnder the 

 influence of strong alkalies; and when mixed with camphor, men- 

 thol, thymol, and similar substances, undergoes a physical change to 

 a liquid. 



Rule 10. Alkaloidal salts are incompatible with — (a) Alka- 

 lies — 'the precipitate is the pure alkaloid, (b) Tannic acid — the 

 precipitate is the insoluble tannate. (c) Iodine, iodides, and bro- 

 mides — precipitate is the iodide or bromide, (d) Mercuric bichlor- 

 ide — the precipitate is the insoluble double salt. 



Quinine in addition is especially precipitated by salicylates and 

 benzoates. 



All these precipitates are more soluble in alcohol than water, so 

 may not show in tinctures and other alcoholic liquids. 



Rule 11. Glucosides are incompatible for the most part with 

 lead acetate and tannic acid, and are decomposed by the mineral 

 acids. 



Experiments : 



Directions -. — T'abulate results and so far as possible give kind 

 of incompatibility and reason for same. 



1. Demonstration : — Rub a little potassium chlorate and tannin 



in a mortar. Students will not perform this experiment. 



2. Add a few drops of concentrated sulphuric acid to a few mils 



pf W9,ter in a test tube. Note any change, 



