442 



SCIENCE 



[N. S. Vol. L. No. 1297 



just disappeared, then weigh the foil again. The 

 difference in weight is due to the volatilized mer- 

 cury. In one instance, 99.83 per cent, of Hg was 

 recovered from HNO3 solution. 



The U. S. P. assay of Donovan's solution: Sig- 

 MUND Waldbott. The TJ. S. P. assay of a certain 

 well-prepared Donovan solution gave far too low 

 results in mereurio iodide contents. Preliminary 

 experiments indicated that the two-fold step in the 

 TJ. ,S. P. determination of mercury involved some 

 loss. A simple method for the determination of 

 mercury in Donovan's solution is proposed, as fol- 

 lows: Precipitate 25 c.c. of Donovan's solution 

 with excess of freshly prepared ammonium sul- 

 phide solution, decant and filter through a double 

 filter, wash, dry at 100° C. and weigh, the two 

 filter papers being previously counterpoised. Two 

 determinations gave satisfactory results. 



The theory of emulsion making: W. D. Ban- 

 croft. 



division or water sewage and sanitation 



Eobert Spurr Weston, Chairman 



W. W. Skinner, Secretary 



Determination of iodid and iromid in mineral 

 waters and brines: W. P. Baughman and W. W, 

 Skinner. 



The determination of hromid and iodid in min 

 eral waters and brines: H. H. Willard and C. C 

 Meloche. The iodid is oxidized to iodate by add 

 ing to the neutral solution of salts a considerable 

 excess of permanganate and boiling for a moment. 

 The solution is cooled, a small amount of hydro 

 chloric acid is added, more than enough to liberate 

 all the bromin and a current of air passed through 

 the hot solution to remove all bromin which is 

 collected in sodium hydroxide, reduced to bromid, 

 precipitated as mixed silver ohlorid and bromid, 

 fused, weighed, fused in chlorin and weighed 

 again. Prom the loss in weight the amount of 

 bromin is calculated. The residue in the retort is 

 treated with alcohol to reduce the excess of per- 

 manganate, and the manganese dioxide filtered off. 

 To the filtrate potassium iodid is added then excess 

 of acid, and the iodine liberated is titrated with 

 thiosulfate. 



The removal of colloidal silicio acid and clay 

 from natural waters: Otto M. Smith. 



A study of well water in a rural community: G. 

 O. HiGLEY. This study was begun because of the 

 fact that the death rate from typhoid in Delaware 

 County was 25.2 per 100,000 of population, as 

 against 6.9 for Cuyahoga County (Cleveland) and 



3.9 for Hamilton County (Cincinnati). The writer 

 with assistants personally visited about 675 homes, 

 noted the condition of the well and surroundings, 

 talked with the people, emphasizing especially the 

 danger if human excreta finds entrance into well 

 water, and took a sample of water in a sterilized 

 bottle for analysis. The tests made were the lac- 

 tose broth and the chlorid tests. About 40 per 

 cent, of the water from dug wells was found pol- 

 luted. As the ©astern half of the county is under- 

 lain with shale, and the western half with lime- 

 stone it was thought that the degree of pollution 

 of well water might be found markedly different 

 in the two sections; however the work is still too 

 incomplete to warrant any report on this point. 



Field methods for the chlorination of small 

 amounts of water: P. E. Georgia. This paper 

 describes conditions of water supply prevailing in 

 the area occupied by the First Depot Division in 

 France. Various methods and devices are de- 

 scribed and illustrated for the continuous chlori- 

 nation of small supplies of water. Some of these 

 devices were constructed in the field from mate- 

 rials at hand. The Lyster bag for water steriliza- 

 tion is described and methods for its use and con- 

 trol are discussed. Tabulations of the bacteriolog- 

 ical results obtained are given. 



The electrostatic precipitation of dust as applied 

 to the sanitary analysis of air: J. Penteado Bill. 

 An apparatus was devised for producing a rectified 

 alternating current of about 20,000 volts. The 

 collector is a 12-ineh piece of aluminum tubing, 

 2i inches in diameter, through which air is drawn 

 by a motor at the rate of 273 cubic feet per hour. 

 Seventy-one tests, each of one hour's duration, 

 were made with this apparatus and a Palmer 

 water spray sampler in the various buildings and 

 departments of a large plant making rubber 

 goods. The following determinations were made 

 for each test: Relative and absolute humidity, 

 barometric pressure, weight of total sediment in 

 50 CO. sample of 100 c.c. aqueous suspension of 

 particles collected in both machines, weight of 

 organic and inorganic fractions of each 50 c.c. 

 sample, the weight of the aluminum collector be- 

 fore testing, with its accumulated dust charge, and 

 with the dust portion still retained after rinsing 

 out to make up a 100 c-o. aqueous suspension. 

 Counts were made on each suspension. The high 

 tension weight figures were reduced to figures com- 

 parable with the rate of air passage through the 

 Palmer machine. The resulting figures when com- 

 pared with the weight figures of the Palmer de- 

 terminations, together with a comparison of the 



