588 EXPERIMENT STATION RECORD. [Vol.37 



pure in the second. With these maximum and minimum values as standards, 

 the relative position of the water under consideration could be determined with 

 ease by the use of the ' percentage of tubes ' scoring method." 



iritra-violet rays, their advantages and disadvantages in the purification 

 of drinking water, R. R. Spencee {Jour. Amer. Water Works Assoc, 4 (1917), 

 No. 2, pp. 112-182, figs. 2). — The author expresses the opinion that the use of 

 ultra-violet rays in the purification of drinking water is capable of further 

 development, with a corresponding increase in efficiency. 



" The method is especially recommended for treating water in circulating 

 systems, in which the water may be exposed many times to the ultra-violet 

 rays. . . , The chief advantages of this method of treatment over chemical 

 methods lie in the fact that objectionable overdosage is impossible. Again, 

 from the standpoint of potability, the water is absolutely unchanged, and, 

 hence, in this respect, is superior even to boiled water. . . . 



" The present forms of apparatus need considerable attention when in opera- 

 tion. Care should be taken to prevent an accumulation of grease or dirt of any 

 kind on the quartz tube. Experience has shown that a very small amount of 

 grease will obstruct the light sufficiently to allow many organisms to pass. 

 Furthermore, the light chamber should be emptied if the machine remains 

 idle for any length of time. This will prevent the growth of algai and other 

 organisms which will obstruct the light when the machine is again op- 

 erated. . . . 



" In the tests [descrii)ed], since the gravity type gave a higher efficiency than 

 the pressure type, and inasmuch as any lamp operating at a higher voltage is 

 known to emit a larger amount of ultra-violet radiation, the use of lamps at a 

 higher voltage, combined with the gravity system, suggests itself as a reason- 

 able line of development. In regard to cost, the method is not expensive when 

 treating relatively small quantities of water." 



Sterilization by liquid chlorin and hypochlorite of lime. !\I. S. Dutton 

 (Jonr. Amer. Water Works Assoc, 4 (1917), A'o. 2. pp. 228-230). — A comparison 

 of calcium hypochlorite and liquid chlorin for water sterilization showed that, 

 " the cost of hypochlorite being considered as 7 cts. per pound and the cost 

 of liquid chlorin as 20 cts. per pound, the average cost of sterilization by means 

 of hypochlorite was $1.07 per million gallons of water treated and 28 cts. per 

 million gallons when using liquid chlorin. The saving, then, in chemicals 

 alone amounted to 79 cts. per million gallons of water treated. 



" In summarizing the results of sterilization, the average reduction in 

 bacteria count of daily plates made on nutrient agar incubated at .37° C. for 24 

 hours was as follows : In January, when hypochlorite was used, the average 

 raw water count was 0,300 and the filtered water count was 1.5. In June, 

 when liquid chlorin was used, the average raw water count was 7,980 and the 

 filtered water count was 11. In Bacillus coli tests, the raw water shows 100 per 

 cent + for both months, while the filtered water shows 1.6 per cent + in Janu- 

 ary and per cent -f in June. These results were obtained by means of 1 cc. 

 samples in all cases. While hypochlorite was used 0.46 parts per million of 

 chlorin was applied and while using liquid chlorin 0.22 parts per million of 

 chlorin was applied." 



The disposal of wastes from the dairy industry, A. E. Kimberly (Ohio 

 Puh. Uealth Jour., 7 (1916), Xo. 7, pp. 250-285, pi. 1; abs. in Cheiti. Abs. 10 

 (1916), No. 21, p. 2779). — This paper reviews existing information on the dairy 

 wastes disposal problem, covering American and foreign experience, and sug- 

 gests practical solutions of given problems, including plant design and estimates 

 of cost. It is based especially on experience by the Ohio State Board of Health. 

 The following conclusions are drawn: 



