§ 7. KE AGENTS. 15 



lution of tlio chlorine begins at common temperatures, but 

 a little heat must be applied after a time. 



7. Cobaltic nitrate. — Co(NOJ.,,— Dissolve the salt in 

 10 parts of water. 



8. Cochineal solution* — Boil cochineal with water. 

 The solution will keep better if about half its volume of 

 alcohol is added to it. 



9. a.— Cupric acetate.— Cu (CJIgOJCuO. (Acetate 

 of copper. Verdigris. 2CuC),CJl303.) — To prepare the 

 solution of this salt for washing the precipitate of baric 

 sulphate, dissolve the commercial salt in water con tabl- 

 ing a little acetic acid, add 2 drops of sulphuric acid, if 

 this acid is not already j^resent, then a few drops of baric 

 chloride until the liquid gives a faint reaction for barium, 

 boil a short time, and filter. The solution should be suffi- 

 ciently concentrated to deposit crystals on cooling. Use 

 the supernatant saturated solution. 



^. Cupric sulphate. — CuSO^. (Sulphate of copper. 

 CuOjSOg.) — This should be recrystallized once or twice. 



10. furcuma-paper. — Turmeric-paper. — Digest pul- 

 verized curcuma root with 6 parts of weak alcohol, color 

 slips of unsized paper with the yellow extract, and dry 

 them. 



11. Ether.— C^H,„0. (C^H^O.)— Tliis is sufticiently 

 pure as obtained of the druggist. 



12. a.— Ferric chloride.— Fe^Clg (Perchlorideofiron. 

 Fe^Clg.) — Its solution should give a permanent precipi- 

 tate with a drop or two of ammonic hydrate ; it should 

 give no blue color with potassic ferricyanide. Dissolve in 

 20 parts of water. 



b. Ferric oxide. — Fe^O.^. (Sesquioxide of iron.) — This 

 is also known as colcothar. 



c. Ferric nitrate.— Fe(N'03) 3. (Nitrate of sesquiox- 

 ide of iron. Fe,03,3N'0^.)— Dissolve iron in nitric acid, 



