268 INTRODUCTION TO GENERAL SCIENCE 



d. Test for borates or boric acid: Treat as in (a) without 

 the addition of ammonium hydrate. If turmeric paper is wet 

 with mixture and turns red upon drying, there is boric acid, or 

 some borate, present. 



e. Test for sulphites or sulphurous acid : odor, that of burn- 

 ing matches. Add little bromine water, and warm. Then add 

 barium chloride solution. White precipitate indicates that 

 there had been some sulphite present. 



/. Test for benzoates or benzoic acid : Add one tenth vol- 

 ume of chloroform and a few drops of sulphuric acid. Do 

 not shake. When chloroform has separated, remove it with a 

 pipette and allow it to evaporate. Crystal plates are formed, 

 and they give off pungent odor when heated. 



196. WATER ANALYSIS 



There are a few simple tests which may be applied to water, 

 and thereby prevent sickness from the use of impure water. 

 It does not follow that clear and sparkling water is pure, nor 

 that muddy water is bad. Chemical tests are the only ones 

 upon which complete dependence may be placed. Even the 

 sense of smell, or that of taste, may pronounce the water bad 

 when the very material which causes the disagreeable effect 

 is beneficial. Naturally, however, pure water contains 

 nothing but air, and our senses do detect some kinds of foreign 

 matter, but not all kinds. Poison from bacterial action can- 

 not be detected, but if the organic material is plentiful in the 

 water, bacterial poisons should be suspected. 



There may be considerable quantities of solid material dis- 

 solved in water and the water still be harmless. Thus no 

 harmful effect has been noticed where hard water has been 

 used for drinking purposes. 



