83 HOW CHOPS GROW. 



NHs + HCl = NH4CI 



Ammonia. Hydrochloric acid. Armnonlum chloride.* 



NHj + CHsCOGH = CHaCOONHj 



Ammonia. Acetic acid. Ammonium Acetate. 



Test for acids and alkalies.— Many vegetable colors are altered by sol- 

 uble acids or soluble bases (alkalies), in such a manner as to answer the 

 pui-pose of distinguishing these two classes of bodies. A solution of 

 cochineal may be employed. It has a ruby-red color when concen- 

 trated, but, on mixing with much pure water, becomes orange or yel- 

 lowish-orange. Acids do not affect this color, while alkalies turn it to 

 an intense carmine or violet-carmine, which is restored to orange by 

 acids. 



Exp. 38.— Prepare tincture t of cochineal by pulverizing 3 grams of 

 cochineal, and shaking frequently with a mixture of 50 c. c. of strong 

 alcohol and 200 c. c. of water. After a day or two, pour off the clear 

 liquid for use. 



To a cup of water add a few drops of strong sulphuric acid, and to an- 

 other similar quantity add as many drops of ammonia. To these liquids 

 add separately 5 drops of cochineal tincture, observing the coloration 

 in each case. Divide the dilute ammonia into two portions, and pour 

 into one of them the dilute acid, until the carmine color just passes into 

 orange. Should excess of acid have been incautiously used, add am- 

 monia, until the carmine reappears, and destroy it again by new por- 

 tions of acid, added dropwise. The acid and base thus nevtralize each 

 other, and the solution contains sulphate of ammonia, but no free acid 

 or base. It will be found that the orange-cochineal indicates very mi- 

 nute quantities of ammo]iia, and the carmine-cochineal correspond- 

 ingly small quantities of acid. 



In the formation of salts, the acids and bases more or 

 less neutralize each other's properties, and their com- 

 pounds, when soluble, have a less sour or less acrid taste, 

 and act less vigorously on vegetable colors than the acids 

 or bases themselves. Some soluble salts have no taste 

 at all resembling either their base or acid, and have 

 no efEect on vegetable colors. This is true of common 

 salt, glauber salts or sulphate of sodium, and saltpeter or 

 nitrate of potassium. Others exhibit the properties of their 

 base, though in a reduced degree. Carbonate of am- 

 monium, for example, has much of the odor, taste, and 



* Also termed ammonic chloride, ammonia hydrochlorate, ammonia 

 hydrochloride, and formerly muriate of ammonia. 



t Tinctures, in the language of the apothecary, are alcoholic solutions. 

 Tincture of litmus (procurable of the apothecary), or of dried red cab- 

 bage, may also be employed. Litmus is made red by soluble acids, and 

 biue by soluble bases. With, red cabbage, acids develop a purpie, and 

 the bases a green color. 



