596 TROPICAL HYGIENE, SANITATION, ETC. 



penetrating and diffusible than chlorine. It is harmless to colour but 

 iron is affected. 



Other means of using formalin are as follows : — 



Mix I42i grammes of permanganate 

 285 ,, formalin 



Put it in a metal tray 7 inches square and 3-4 inches deep for the combustion 



The Formanganate process consists of : — 



16 oz. of 40 per cent, formaldehyde solution 

 240 grammes of permanganate for each 1,000 cubic feet 

 Warmth to 63'' F., and moisture to 60-65 per cent, humidity are essential. 

 A " homely " method is to use 8oz. of permanganate for each pint of formaldehyde 

 for every 1,000 cubic feet of air space. Suspend wet sheets in the room. All fires 

 should be extinguished as the gas is slightly inflammable. 



(3) Chlorine. 



Chlorine is produced by adding crude hydrochloric acid to calcium 

 chloride, ij to 2 pints of the acid to each pound of lime. Two pounds 

 of calcium chloride with three pounds of the acid for each 1,000 cubic 

 feet are generally used. 



Nitrous fumes are generated by adding copper filings to nitric 

 acid. 



Some medical officers have found useful the following for the 

 destruction of mosquitoes : — 



Crenyl or creolin vaporized by a spirit lamp. 



Use 600 c.c. for a room of 100 cubic metres with 270 c.c. of alcohol. 



It is not necessary to paste up all the cracks. 



It should be left for eight hours. 



It is cheap, there is no smoke, it does not damage objects and does 

 not have the bleaching effect of sulphurous acid. 



In Great Britian rats do an enormous amount of damage reaching 

 the sum of ;^' 10,000,000 per annum. 



For rat extermination viruses are sometimes used, e.g., the Liver- 

 pool virus, the Danysz virus and Ratin at a comparative cost of i, iJ 

 and 2^, but they rapidly lose their virulence in the tropics. 



Barium carbonate, i in 4 of meal on fish or bread, is effective 

 against rats and mice. 



Warehouses and stores should be disinfected with Clayton's 

 apparatus every two months. 



QUARANTINE. 



Land quarantine was abolished in Europe some time ago but the 

 governments have the right to close the frontiers if necessary. 



The International Regulations of the Paris Convention of 1903 

 were formed to prevent the importation of cholera, plague and yellow 

 fever. 



These are the onlv diseases as vet under international control. 



