February 22, 1912] 



NATURE 



55: 



new ozone plants are being installed in Paris with a 

 daily output of 45,000 cubic meters of water. 



In the United States ozone is employed at Phil- 

 adelphia. The water ozonised is from the River 

 Schuylkill in West Philadelphia. This is extremely 

 impure, and is said to contain 2,500,000 bacteria per 

 cubic centimetre. After treatment the number is . re- 

 duced to 25 per cubic centimetre. The Bacillus coli 

 which previously abounds is completely destroyed. The 

 colour of the water is improved and its offensive 

 odour removed. 



It is obvious from the foregoing that the employ- 

 ment of ozone for sterilising water is now being car- 

 ried out on a very considerable commercial scale, and 

 it is found not only efficient but also very cheap. In 

 this country to sterilise 1000 gallons of water the cost 

 is from one halfpenny to one penny, depending upon 

 the size of the plant and the cost of the electrical 

 power. In connection with the sterilisation of water, 



A new method for production of ozone in large 

 quantities has just been described by E. H. Archibald 

 and H. von Wurtenberg. Dilute sulphuric acid is 

 electrolysed with a direct and alternating current. The 

 alternating current acts as a depolariser, and the pro- 

 duction of ozone is 300 times greater than with a 

 direct current only. The maximum yield was obtained 

 with an alternating current of 6 amperes and a con- 

 tinuous current of 0*25 to i ampere. Increase in the 

 frequency of the alternating current increases the 

 ozone yield. 



Before leaving the question of water sterilisation 

 another method which is now being employed should 

 be mentioned. It has been found that the ultra-violet 

 rays are very eflRcient for sterilising water. The rays 

 are produced by a mercury- vapour arc enclosed in a 



A, 7AmlNLET 



• n-^ Valve , 



Pipe Convevihg Wa ter Ozone Pipe 

 ToAtomisers 



■y ' " 



6. Expansion 

 I Chamber 



Water 

 Control 

 Valve 

 2 Motor 

 Driving Pump. \ 



3.Water SrsRiusiNG Toiler 



it should be mentioned that it is an easy matter by 

 means of petrol motors to use ozone for sterilising 

 water during campaigns. Indeed, during the Russo- 

 Japanese war a portable plant supplied by Messrs. 

 Siemens and Halske was employed with great success. 

 The apparatus consists of two small wagons, each of 

 which is hauled by one horse. The small dynamo 

 and all the pumping appliances, &c., are worked by 

 means of a petrol motor. , . , r c ■ 



. Ozone apparatus have also been devised for httmg 

 on to the ordinary water mains, the ozoniser only 

 functioning when the water tap is turned on. Ihe 

 water passes through a special form of mjcctor which 

 causes a thorough admixture with the ozone. At the 

 moment the water is drawn off it smells of ozone, but 

 [within a few minutes the odour has gone off, and 

 ithe water is fit for drinking purposes. 'I his form of 

 [ozoniser is very useful in hospitals and other public 

 "institutions. 



NO. 2208, VOL. 88] 



quartz tube. Under the influence of the rays from a 

 niercury-vapour lamp of silica with a current of 

 3 amps, at 220 volts B. coli are killed in 



I >econd ai a distance of 10 cenlimclre* 

 4 seconds ., ,• 'o »• 



15 ,. .. .. 40 



30 „ .. .. *>° 



Where water is to be sterilised it is necessary (or it 

 to be clear, because the ultra-violet rays are very 

 rapidly absorbed. This is particularly the case if water 

 contains colloids. The various classes of n)'crobes 

 arc not equally sensitive; e.g. conditions which kill 

 staphylcoccus in five seconds will kill cholera in from 

 twenty to sixtv seconds. 



Lamps of glass are useless, because the glass 

 absorbs a great portion of the rays. tig. 5 shows the 

 construction of the apparatus for water stenl.sat.on 

 brought out bv the Cooper-Hewitt Wcst.nghouse Co. 



