FOOD 131 



mine on what the discoloration depends. But, in any case, it must be 

 clearly understood that the colour in itself is not a satisfactory indication 

 of the quality of the fluid. 



The brightest and most sparkling water may be absolutely deadly, while 

 dark-coloured and dirty water may be comparatively harmless. 



A rough test, which the unprofessional observer can easily employ, 

 is to allow the specimen of water to stand in a glass for some hours, for 

 the purpose of ascertaining if there is any sediment. Taste and smell 

 are means of ascertaining something of the qualities of water, as in a 

 wholesome state the fluid does not possess any decided taste, either acid or 

 alkaline; and an odour, either pungent or offensive, may be at once accepted 

 as proof that the water is not fit for drinking purposes. Then there are also 

 certain simple tests which may be readily employed even by a person who 

 has not more than a very elementary knowledge of chemistry. For example, 

 the presence of lime may be detected at once by adding a solution of oxy- 

 late of ammonium, which causes at once a white precipitate, and some idea 

 may be formed of the amount by the quantity of precipitate which falls. 

 A mere turbid condition, rendering the water somewhat opalescent in 

 appearance, does not indicate that the water contains more than an ordinary 

 quantity of lime, while a large quantity of precipitate indicates a hard water. 



Colonel Fred. Smith gives a very simple process, which he has 

 found effectual in estimating in a rough way the amount of hardness 

 of water in which the oxylate of ammonium has caused the characteristic 

 white precipitate. He proposes to use the ordinary soap liniment as a 

 test, and he finds that 1 drop of this preparation added to ^ oz. of 

 water will indicate about 1^ grain of lime per gallon, if on shaking the 

 mixture a lather is produced. 



If, however, 4 drops are required to produce a lather there will be about 

 6 grains of lime per gallon. If 6 drops are required there will be 9 grains, 

 if 12 drops, 18 grains. Calculating that the amount of lime per gallon in 

 good water should not exceed 6 grains, it is easy to form some idea of the 

 degree of hardness which exists in the water under examination. The 

 process may be further extended in order to ascertain which of the lime 

 salts is the cause of the hardness; which may depend upon carbonate of 

 lime, and indeed generally does, but may also result from the presence 

 of a sulphate, chloride, or nitrate. The presence of the carbonate is deter- 

 mined accurately by boiling a portion of the water which has been tested 

 by the soap liniment. Supposing that it takes 12 drops of soap liniment 

 to produce a lather before boiling, and only 3 drops to produce the same 

 effect after the water has been boiled, it would show that the hardness was 

 due to chalk (calcium carbonate). The advantage of acquiring this know- 



