Januaey 11, 1907] 



SCIENCE 



65 



which are usually regarded as water bacteria, 

 are extremely sensitive; Bacillus typhi and 

 Bacillus coli seem somewhat between the two 

 extremes. 



Emphasis should be laid upon the intimate 

 relation between sewage disposal and water 

 purification. Proper sewage disposal, whether 

 the varying conditions mean that this should 

 be interpreted as sterilization or merely slight 

 improvement, is logically the first step in the 

 problem of securing and maintaining a safe 

 and potable water supply. 



The use of copper in sterilizing a sewage or 

 in improving the quality of the effluent from 

 a sewage purification plant is in many ways 

 comparable to the use of copper for the pur- 

 pose of removing pathogenic bacteria in a 

 municipal water supply. Briefly, the use of 

 copper in sewage treatment should be re- 

 stricted to occasionally treating crude sewage 

 from small communities where the initial ex- 

 pense of installing a sewage disposal plant is 

 prohibitive, in improving the effluent of sew- 

 age disposal plants of poor quality and in the 

 emergency of an unusual and serious accident 

 to a sewage disposal works. 



M. C. Mabsh, 

 Recording Secretary 



THE AMERICAN CHEMICAL SOCIETY 

 NORTHEASTERN SECTION 



The seventy-second regular meeting of the 

 section was held in the rooms of the Trade 

 Club, 77 Summer Street, Boston, on Friday, 

 December 21, with President L. A. Olney in 

 the chair. About forty-five members were 

 present. 



Dr. W. C. Bray, of the Eesearch Labora- 

 tories of the Massachusetts Institute of Tech- 

 nology, presented a paper by Professor Arthur 

 A. Noyes and himself upon 'An Improved 

 Scheme of Qualitative Analysis for the Tin 

 Group, including the Detection of Platinum, 

 Gold, Selenium, Tellurium and Molybdenum.' 

 The work upon which the paper was based was 

 begun at the Massachusetts Institute of Tech- 

 nology some six years ago, under Professor 

 Noyes's direction, and has been continued to 



the present time. The analytical scheme is 

 to be universally applicable, and to include all 

 the elements. It will permit of the detection 

 of quantities as small as one or two milligrams 

 of any element in a mixture. The innovations 

 of the system are especially this quantitative 

 character of the work and the systematic 

 method devised for preparing the solution of 

 the substance for analysis. In this paper only 

 that part of the scheme which related to the 

 tin group was considered. It was shown that 

 in the cases of the sulphides of arsenic, anti- 

 mony and tin, 1 milligram of any one of the 

 three, could be detected in the presence of 

 500 milligrams of either of the others. In 

 the case of platinum, gold, selenium, tellurium 

 and molybdenum, the quantities which could 

 be detected ranged from one half to one milli- 

 gram in 500. Confirmatory tests have been 

 introduced in all cases where the original test 

 might be misinterpreted through faulty work 

 on the part of the analyst. Demonstrations 

 of several of the tests were made, to show the 

 characteristic reactions : Thus, the separation 

 of selenium and tellurium by solution in con- 

 centrated hydrochloric acid, and reduction 

 and precipitation of the selenium in the cold 

 solution by sulphurous acid — a bright red pre- 

 cipitate separating. The tellurium may then 

 be precipitated by diluting the solution and 

 adding potassium iodide, whereby a black pre- 

 cipitate falls. The precipitation of gold by 

 means of oxalic acid, yielding a purple precipi- 

 tate, and the detection of molybdenum by use 

 of potassium sulphocyanide and metallic zinc, 

 whereby a brilliant red color was obtained, 

 which soon faded to pale yellow as the re- 

 ducing action of the zinc continued, were also 

 shown. In the discussion of the paper the 

 speaker brought out certain objections to the 

 usual Marsh test, and showed the advantages 

 of the proposed procedure, in which the mag- 

 nesium-ammonium arsenate precipitate is re- 

 dissolved in hydrochloric acid, and the arsenic 

 again thrown out with hydrogen sulphide. 

 The method of separating tin and antimony 

 was also dwelt upon. 



Frank H. Thokp, 



Secretary 



