SIMPLE TESTS FOR WATER. 395 



Tests for alkalies or alkaline earths. — Take a piece of r^-^f litmus paper 

 (blue litmus paper that has been reddened by means of vinegar or other weak 

 acid), and immerse it in the water. If the blue color of the paper is restored 

 then the water contains either a free alkali or alkaline earth. If the blue color 

 disappears from the paper after a short exposure to the atmosphere the presence of 

 " volatile alkali " (ammonia) is indicated. If a litde syrup of violets is added to 

 water which contains a free alkali or alkaUne earth it will become green. 



Tests for iron. — To a glass of the water add a few drops of infusion of 

 nutgalls, or suspend a nutgall in it, by means of a thread, for twenty-four hours. 

 If iron be present the water will become of a dark brown or black color. Yel- 

 low prussiate of potash (Potassium Ferrocyanide) is a still more delicate test for 

 detecting iron. If a crystal, or a drop of its solution in water, be added to a 

 glass of water containing iron, it will immediately become of a blue color. 



Test for chlorides and salts of hydrochloric acid. — Let a few drops 

 -of nitrate of silver solution fall into a glass of the water. If a milkiness be pro- 

 duced, which disappears on the addition of a little ammonia solution, it may be 

 concluded that chlorides or some salts of hydrochloric acid are present. (Hydro- 

 chloric acid was formerly called muriatic acid). Chloride of calcium, chloride o^ 

 sodium (common table salt), and chloride of magnesium are most commonly to 

 be met with in spring water. 



Test for magnesia. — Take a quantity of the water and boil down to one- 

 twentieth part of its bulk. Drop a few grains of carbonate of ammonia into a 

 ■small glass of the water, and add a small quantity of phosphate of soda; if any 

 magnesia be present it will fall to the bottom of the glass as a white precipitate. 



For this experiment the carbonate of ammonia must be in a neutral 'aX.dXo. \ if 

 exposed to the air this salt rapidly becomes acid. 



Test for free lime. — Into a glass of the water drop a crystal or two of 

 oxalic acid. If a precipitate takes place, and if another glass from the same 

 sample becomes milky upon blowing air from the lungs into it through a quill or 

 glass tube, the presence of free lime or baryta may be inferred. The latter has 

 never been found /r<f(? in water. 



Test for carbonic acid — Take a quantity of the water and add to it an 

 equal quantity of perfectly transparent lime water. If carbonic acid be present, 

 either free or combined, a white precipitate immediately appears, which, on add- 

 ing a few drops of hydrochloric acid, is dissolved with effervescence. 



Test for any combination of sulphur. — Put a little mercury into a vial, 

 filled with the water to be tested, cork it, and let it stand for a few hours. If 

 the surface of the mercury has acquired a black appearance, and a blackish pow- 

 der separates from it on shaking the vial, the presence of sulphur may be inferred. 



Test for lead. — To a little of the water in a glass add an equal quantity of 

 sulphureted hydrogen solution (water impregnated with hydrogen sulphide gas). 

 If lead be present the water will assume a dark brown or blackish tinge. Lead 

 may also be detected by adding a little of a solution of sulphide of potash, or 

 sulphide of ammonia; a similar effect will take place if lead be present. 



