98 



SCIENCE 



[N. S. Vol. XLII. No. 1072 



F. W. Beuckmillee: The Use of Bensidene for 

 Sulfates in Water Analysis. 



Edwaed Baetow and A. N. Bennett: The Deter- 

 mination of Arsenic in Filter Alum. 

 European specifications require that filter alum 

 be free from arsenic. This suggested an investi- 

 gation of filter alum used in the United States. 

 Samples collected from plants in Illinois showed 

 not more than 4 parts per million of As-Oa. Since 

 the Illinois plants are supplied from western man- 

 ufactories, samples were obtained from plants 

 throughout the east. Larger amounts of arsenic 

 were found in some of the specimens obtained. 

 Only traces of arsenic were found in water treated 

 with alum, containing the highest amount of ar- 

 senic found. While this would indicate a strong 

 possibility that the presence of arsenic in filter 

 alum is not significant, the authors would recom- 

 mend that preference be given to alums with a low 

 arsenic content. 



C. P. HoovEE: The Manufacture of Alum at the 



Columbus Water Softening and Purification 



Works. 



The process most generally employed to-day for 

 coagulating and purifying water contemplates ap- 

 plying to the water under treatment a solution of 

 aluminum sulfate. The cost of this chemical varies 

 from $17 to $20 per ton. 



A plant for making alum has recently been built 

 and put in service at the Columbus Water Purifi- 

 cation Plant. This is the first plant of its kind 

 ever built at a water purification works for making 

 alum to coagulate water, and, although it has only 

 been in operation a short time, it has been a success 

 both technically and economically. The process is 

 short, simple and inexpensive, because it consists 

 simply in boiling bauxite with sulfuric acid and 

 applying the resultant solution to the water under 

 treatment, thus eliminating five distinct steps in 

 alum-making, namely: filtering, concentrating, 

 crystallizing, grinding and redissolving. An invest- 

 ment of $12,000 was required for its construction, 

 and it has been conservatively estimated that 

 $6,000 per year will be saved the city in the cost of 

 alum. Between 800 and 1,000 tons of alum will 

 be manufactured during the coming year at a cost 

 of about $10.50 per ton. 



Abthue Ledeeer: Determination of the Biochem- 

 ical Oxygen Demand iy the Saltpeter Method in 

 Stockyards, Tanneries and Corn Products Waste. 

 The saltpeter method was originally described by 



Lederer in the Journal of Infectious Diseases, 14: 



482 (1914). In short, the method depends upon 

 the denitrification of a sodium nitrate solution when 

 incubated for a definite period (10 days at 20° C, 

 or 5 days at 37° G.) with sewage or polluted water. 

 The residual nitrite-nitrate oxygen is determined 

 analytically. The method permits a comparison of 

 the strength of sewages from the deoxygenation 

 standpoint. The oxygen demand of domestic sew- 

 ages usually varies between 100 and 300 p. p. m. of 

 oxygen. The method can be applied to slaughter- 

 inghouse wastes without modification. The oxygen 

 consumption of the Chicago stockyards waste in the 

 Center Av. sewer fluctuates around 1,000 p.p.m., 20 

 per cent, of which is consumed during the first 

 twenty-four hours. The oxygen demand of com- 

 bined corn products waste fluctuated between 400 

 and 1,200 p.p.m., approximately 7 per cent, of 

 which was used up in the flrst twenty-four hours. 

 In this and in tannery waste the presence of lime 

 or acid should be guarded against. If free lime is 

 present it must be neutralized with dilute hydro- 

 chloric acid previous to incubation with sodium ni- 

 trate. If acid is present neutralize with sodium 

 bicarbonate. The oxygen demand of a calfskin 

 tannery waste investigated fluctuated between 400 

 and 1,000 p.p.m., 7 per cent, of which was used up 

 in the first twenty-four hours. If a waste is sterile 

 or devoid of sewage bacteria "seed" it with a few 

 c.c. of sewage or polluted water. The general prin- 

 ciples brought out in the work with the wastes men- 

 tioned can be applied to other wastes. 



Eaele B. Phelps : Ventilation Studies. 



Edwaed Bartow and F. W. Mohlman: Purifica- 

 tion of Sewage hy Aeration in the Presence of 

 Activated Sludge. 



Domestic sewage from the city of Champaign 

 has been treated according to the method sug- 

 gested by Ardern and Lockett.s When raw sewage 

 is aerated without the addition of sludge am- 

 monium nitrogen is replaced by nitrite nitrogen, 

 the nitrite nitrogen in turn being replaced by ni- 

 trate nitrogen. In the presence of sludge, the ni- 

 trite nitrogen is never present in large quantities. 

 Ammonium nitrogen is apparently changed di- 

 rectly to nitrate nitrogen. The time of nitrification 

 is reduced from fifteen days to four hours. The 

 predominant organism in the sludge is an annelid 

 worm, known as Aeolosoma hemprichi, although 

 other microscopic animals are present. The sludge 



3 Jour. Soc. Chem. Ind., 33: 523-39; 1,122-24. 



