640 



SCIENCE 



[N. S. Vol. LIV. No. 1408. 



unaffected by the metal ion, but that the inflection 

 point occurs at a slightly lower hydrogen-ion con- 

 centration in dilute solutions than in the more con- 

 centrated ones. Precipitation curves of the pre- 

 cipitation of calcium as the carbonate while not as 

 regular as those obtained in the precipitation of 

 magnesium, tend to show that the reaction is com- 

 plete, sufficient carbonate being present, at a hydro- 

 gen-ion concentration corresponding to pH of 9.5. 



Study of the Weazelszky method for the determi- 

 nation of iodide and 'bromide: "W. E. Shaefek and 

 J. "W. Sale. The Weszelszky method has been care- 

 fully tested. The kind and quantity of absorbing 

 alkali and the time and temperature used to remove 

 the chlorate were varied until satisfactory condi- 

 tions for the recovery of bromiae from bromine 

 water were found. A modified absorption appa- 

 ratus was constructed and the kind and concentra- 

 tion of the acid added to the reaction flask varied 

 in an effort to recover bromine quantitatively from 

 potassium bromide and estimate it by the method 

 found to be satisfactory. Iodine was converted into 

 iodic acid by chlorine water in the reaction flask 

 and estimated in solutions of various acid concentra- 

 tions. A rapid and satisfactory modified Wes- 

 zelszky method for the determination of small 

 amounts of iodine based on these experiments is 

 given. The Weszelszky method for bromide in the 

 presence of iodide, however modified, is incapable 

 of giving satisfactory results on small samples and 

 its use is not recommended. 



Purity of bottled mineral waters: W. W. Skin- 

 ner AND J. W. Sale. During the past year, the 

 Water and Beverage Laboratory of the Bureau of 

 Chemistry has made sanitary inspections of about 

 seventy-five springs and wells, located in ten states. 

 These inspectors uncovered numerous unsuspected 

 sources of pollution of which specific examples are 

 described. Samples of water from interstate ship- 

 ments and from shipments offered for entry into 

 the U. 8. are also analyzed for their purity. In the 

 last six years over 4,000 bottles were opened and 

 the water examined. Shipments of polluted water 

 are either refused entry in the case of foreign 

 waters or are condensed and destroyed in the ease 

 of domestic waters. 



Commercial peptones and the culture media used 

 in the examination of water: E. M. Chamot and 

 F. B. Georgia. Titration curves of the following 

 peptones are shown: Witte; Bacto (Digestive Fer- 

 ments Company) ; Proteose (Digestive Ferments 

 Company); Armour's; Parke, Davis Company; 

 Fairchild Brothers and Foster; and Stearns. The 



peptones are grouped according to relations shown 

 by these curves. The optimum reaction (Ph) using 

 a culture of B. coli is given for each peptone. This 

 is determined by attenuating the culture by ex- 

 posure to a suitable dOution of phenol and inocula- 

 ting a series of tubes containing the peptone solu- 

 tion adjusted to various Ph values at definite time 

 intervals and noting the Ph value in which growth 

 is obtained after exposure of the culture to the 

 phenol for the longest period of time. It is shown 

 that Witte, Bacto, Proteose, Armour's, and Parke, 

 Davis and Company Peptones give optimum growth 

 when unadjusted or but very slightly adjusted. 

 With Fairchild Brothers and Foster 's and Stearns 's 

 peptones it is necessary to adjust the reaction to a 

 Ph value slightly above, 5.7. It is shown that the 

 optimimi Ph value for B. coli in peptone KCl solu- 

 tion varies over a considerable range and depends 

 on the peptone used. The introduction of lactose 

 into the medium changes the optimum Ph value. 



A study of the activated sludge process: J. A. 

 Wilson, W. E. Copeland and H. M. Heisig. 



Mineral composition of the water supply of 

 seventy cities in the United States : J. W. Sale and 

 W. W. Skinner. The paper develops the fact that 

 statistics showing the mineral composition of the 

 water supplies of even the larger cities in the 

 United States have not been compiled heretofore, 

 although the matter is of considerable interest par- 

 ticularly to physicians and to the traveling public. 

 Seventy analyses obtained from city ofiieials have 

 been reduced to a common basis for comparison 

 and tabulated. Of the cities mentioned, Atlanta, 

 Ga., has a water supply which contains the smallest 

 amount of dissolved mineral matter, while Okla- 

 homa City, Okla., has a water supply which con- 

 tains tie largest amount of dissolved mineral 

 matter. 



Quantitative versus qualitative adjustment of the 

 H-ion concentration of culture media: Geo. C. 

 Bunker and Henry Schuber. The reactions of 

 culture media prepared in. the laboratories of water- 

 works are determined by one of the following three 

 methods, of which the first two may be classed as 

 loose and the third as approximate in reference to 

 their precision. (1) By titration with phenolphtha- 

 lein, (2) with phenol red or with brom thymol blue 

 and (3) by comparison of a portion of the medium, 

 to which a suitable indicator has been added, with 

 color standards of definite H-ion concentration. 

 The methods are discussed. 



Charles L. Parsons, 



Secretary 



