558 TROPICAL HYGIENE, SANITATION, ETC. 



Peaty waters containing acids from moorlands cause plumbo- 

 solvency. 



Lacmoid Avill become reddenea in such waters, thus indicating 

 their presence. jNIanganese oxide on the fiUer beds is etMcacious. 



Thermal. 



Boiling destroys all living organisms and reduces hardness but the 

 difficulty is with cooling afterwards. Earthernware vessels placed in 

 an air current are useful for this purpose. The flat taste can be 

 removed b_v oxidation. Weak tea is advisable for travellers for 

 reasons previousl}' described. 



Heat has been used to sterilize water under pressure so that no 

 gases are lost; the cool water passing in being used to cool the water 

 passing out, but the process is expensive when used on a large scale. 

 The pipes are readily occluded when the Avater is hard. A number 

 of inventions are on the market for this purpose. 



The Maiche Automatic Sterilizer is serviceable. It cost (pre-war) 

 ;^56, uses 5 gallons of kerosene weekly, cost of maintenance is Qd. 

 daily, and it produces 800 to 1,000 gallons of sterilized water per diem. 



The oil lamp is filled twice daily, otherwise it is left to work 

 automatically. 



Steam pipes conveying steam to water tanks will sterilize the water, 

 after which the water can be left to cool. 



Distillation is of universal application and is essential for all 

 important ships as sea water can be utilized bv these means. 



The flat taste is removed by the water falling through a sieve or 

 by charging it with carbon dioxide under pressure. 



Electrical. 



Ultra-violet rays, generated by a quartz mercury vapour lamp, are 

 now used as sterilizing agents. Courmont and Nogier found that 

 when a Kromayer lamp was immersed in water containing 1,000,000 

 bacteria and 100,000 B. coli per c.c. that it was completelv sterilized 

 in one minute. Previous filtration is almost obligatory as suspended 

 and colloidal matter nullifies the action. 



Thresh and Beale found that a small Cooper Hewitt quartz lamp 

 would purify 50 to 200 gallons per hour. At Luneville in France, 

 there was an installation a\ ith a ten-lamp canal which has practicallv 

 banished typhoid from the city. 



The energy required is from 50 to 130 units per million gallons 

 of water. A portable apparatus is now on the market. 



Filtration. 

 A. Domestic Filtration. 



The Pasteur-Chamberland porcelain filter and the Rerkefeld filter 

 of diatomaceous earth are the best. 



