WATER 557 



A portable petroleum-driven motcr and apparatus is on the market 

 which is capable of sterilizing 400 to 600 gallons per h(jur equivalent 

 to 3 cubic metres. This is very suitable for troops. 

 Like most processes it has its disadvantages, e.g., 

 (i) The water often accjuires a disagreeable taste. 



(2) Nitrous acids are often produced along with the ozones. 



(3) The initial cost is considerable. 



(4) Skilled supervision is necessary. 



Permanganate of potash, i in 4,000 or 4 ounces (113 grm.) for an 

 ordinary well is sufficient. It is useful for cholera-infected wells. 



The water should remain pink for half-an-hour afterwards. 



Alum will remove the excess of colour. It will also remove the 

 odour of offensive-smelling waters. For smaller quantities, boil the 

 water and then add the permanganate until a pink tinge remains for 

 thirty minutes. 



The Compound Tablet is now in use and has proved its worth. 



The ing-redients of these tablets varv but that of Vaillard is a 

 good preparation : — 



(i) Blue tablet contains: Pot. iodide, o'l grm., sod. iodide, 

 o"oi56 grm., and of methylene blue, a sufficiency. 



(2) Red tablet contains: Tartaric acid, o-ioo grm., fuchsin, a 

 sufficiency. 



(3) White tablet contains: Sodium hyposulphite, o-ii6 grm. 



To one litre of water add one tablet of Nos. i and 2. As a result 

 of this o-o6 o-rm. of free iodine is liberated which sterilizes the water 

 in fifteen minutes. Then add a white tablet which neutralizes the 

 free iodine. The resulting water is colourless and odourless. 



Ova and probably parasites are not destroyed by it. 



Liquid chlorine has been used for the troops in the field. 



I '50 grm. of chlorine for 50 gallons of water. 



Then sodium sulphite, 36 grm. are added to neutralize the 



chlorine. 



The gas disappears spontaneously in twenty-four hours, after which 

 period no sodium sulphite is required. The cost is low, only id. per 

 500 gallons. 



Copper sulphate is used, i in 1,000,000 to : — 



(i) Clear rivers and lakes of algas. 



(2) Kill mosquito larvae in water tanks. 



(3) To rid waters of odours arising from micro-organisms and alg^e. 

 F'ishes are killed by it. 



Chalk, finely ground, is used, one grain (o'o6 grm.) per gallon. 

 It prevents plumbo-solvency where this may take place. THp 

 water must then be filtered and lime water added. 



