CIIKMISTRY. 



121 



se ions are always colorless can be arranged in 

 vertical lines. so that the horizontal lines contain 

 each a natural group; also that the elements u 

 ions are always colored form series with the atomic 

 weights immediately following one another. If 

 the atomic weights in the first vertical column are 

 subtracted from those in the second, those in the 

 .d from those in the third, and so on. certain 

 standard differences are found to recur. One of 

 tlie.-e is about 16. the other about 46. and the third 

 about ss. The elements with ions always colored 

 utside of this rule. Their behavior is alto- 

 gether anomalous. The colorless elements, begin- 

 ning with hydrogen, fall into four series of nine 

 each, interrupted by four colored groups, and fol- 

 lowed by an alternate series, Hg. Ti, Pb, Bi, Th, 

 and C. 



In long-continued studies of the atomic weight 

 of oxygen. Dr. E. W. Morley used two methods for 

 determining the ratio between it and hydrogen : 

 those of actually weighing the gases and of synthe- 

 tizing water. He also dealt with much larger vol 

 nines of purer gases than previous experimenters 

 had used. His experiments all bear the marks of 

 extreme accuracy. Collating all the results of his 

 experiments, he gives the following values: Weight 

 of 1 litre of oxygen, 1'42'JUU: weight of 1 litre of 

 hydrogen, n-n^is;:; : atomic weight of oxygen (chem- 

 ical method). lo'8?'J: molecular weight of oxygen 

 (chemical method), l.r s ?U ; atomic weight of oxygen 

 (physical method). 1-V>7'.'. 



In a new determination of the relative atomic 

 weights of oxygen and hydrogen, by Julius Thom- 

 sen, the hydrogen was evolved by means of strong 

 potash and metallic aluminium, and the amount of 

 the element used was determined from the decrease 

 in weight of the apparatus. The result given by a 

 series of experiments was H : :: 1 : 15'8690 O'OO^. 

 It agrees with remarkable closeness with the results 

 obtained by Cooke and Richards, Rayleigh and 

 t, Morley, Xoyes, Ditmar and Henderson, and 

 Leduc' The author believes that the ratio is now 

 settled within very close limits. 



Chemical Analysis. A volumetric method for 

 lead analysis, by Alfred C. Beebe, of Chicago, de- 

 pends upon titrating a solution of acetate of lead 

 free from alkali salts by means of ferrocyanide of 

 potassium, using a saturated solution of uranium 

 acetate as an indicator. The end reaction, which 

 is formed by adding a drop of the solution, being 

 titrated to the uranium solution on a porcelain 

 plate, is a delicate pink, changing, after standing 

 time, to -In-own. The ferrocyanide solution 

 can be standardized with either lead sulphate or 

 lead acetate. The uranium-acetate solution should 

 have a little free acetic acid in it, or the sharpness 

 of the end reaction is affected. 



As an extremely delicate test for the detection of 

 minute quantities of mercury in cases of poi>onin:r. 

 D. Vitali puts the supposed solution of mercury into 

 a minute porcelain capsule, in which are immersed 

 small pieces of sheet.gold and small iron tacks. The 

 mercury present in the solution deposits itself upon 

 the gold, and partly upon the tacks. After about an 

 hour the fragments of the two metals are withdrawn 

 from the liquid, washed, dried, and heated to faint 

 redness. The mercury forms a gray coating near 

 the heated part of the glass. The fragments of iron 

 and gold are then taken out and a crystal of iodine 

 is put in and heated, when the iodine vapors in con- 

 tact with the mercurial coating form a yellow ring, 

 which passes into the red of mercuric iodide. If 

 the iodine is in excess a brown ring is formed. By 

 this process. O00001 gramme of mercury can be recog- 

 nized. The mercury deposited on the metals may 

 also be shown by placing the washed and dried por- 

 tions of gold and iron in a porcelain capsule, mois- 



tened witli a solution of gold chloride, and heating. 

 However minute a quantity of mercury has b./'-ii 

 attached to the metals, the inner surface of th- 

 per capsule displays a violet-blue color, arising from 

 the reduction of gold occasioned by the mercurial 

 vapors. 



The rapid process of R. Engel and J. Bernard for 

 the determination of ar>enic depends on the prin- 

 ciple that the oxygen compounds of arsenic in solu- 

 tion in concentrated hydrochloric acid are entirely 

 reduced by hypophosphoroua acid to the state o'f 

 nonmetallic arsenical compound; and that the 

 nonmetallic arsenic (that is, arsenic in combination 

 with a nonmetallic element) is transformed by 

 iodine in solution into arsenious acid, with the for- 

 mation of merely small quantities of arsenic acid. 

 In a liquid rendered alkaline by bicarbonates the 

 transformation into arsenic acid' is total. 



While tartaric acid is easily distinguished by the 

 insolubility of its potassium" salt in a mixture of 

 alcohol and ether, the other acids, especially citric 

 and malic, often present in vegetable tissues, are 

 more difficult to recognize. M. L. Lindot. in study- 

 ing the compounds of these acids with quinine aiid 

 cinchonine. has found that the resulting salts, 

 cially the acid salts, present differences in solubility 

 in methylic alcohol, by means of which malic and 

 citric acids may be easily distinguished and sepa- 

 rated from vegetable juices. Quinine dissolved in 

 methylic acid precipitates citric acid, and the like 

 solution of cinchonine precipitates malic acid under' 

 identical conditions. 



A contribution to the discussion as to the relative 

 merits of the chemical and the bacteriological 

 methods of water analysis is made by W. P. Mason. 

 A case is cited in which water, otherwise pure, 

 which had been purposely inoculated with typhoid 

 germs was pronounced pure by a famous chemist. 

 Such a sample of water. Mr. Mason says, could not 

 lie found in practice, and the very conditions under 

 which it was prepared eliminated the chemical 

 items indicating pollution, " while it increased tre- 

 mendously the signs governing the bacteriological 

 side of the case. The chemist looked in the water 

 for sewage, which, as it means in practice, contains 

 an immense amount of material other than that pro- 

 ductive of disease, and it is upon just this compara- 

 tively harmless, but constantly present material that 

 the chemist relies for the indication on which he 

 l>u->-> his opinion. He is unable to say whe'her or 

 not the sewage-laden water is disea-v-bearing at 

 any particular date, for to him all sewage is alike; 

 but he condemns the water, for the reason that, 

 although it may be harmless to-day, it is impossible 

 to predict what may be its condition to-morrow. 

 In the matter of determining the suitability of a 

 stream for city supply, the services of a bacteriolo- 

 gist should be unquestionably secured, but it is 

 doubtful if his report can be considered of more 

 importance than that of the chemist. Chemistry 

 anticipates what may happen in the future, and by 

 timely advice may prevent an outbreak of di> 

 while the discovery of disease germs in the water is 

 'le only after the water has become infected. 

 Bacteriology is of especial value and greatly su- 

 perior to chemistry for the testing of filters and 

 watching any variation in their efficiency. 



The gray matter which is left after repeated re- 

 actions of cuprous oxide on silver nitrite has been 

 found by Paul Sabatier to contain a cuprous nitrite, 

 and when treated with an excess of concentrated 

 sulphuric acid, dissolves in it. developing magnifi- 

 cent violet-blue coloration, which is immediately 

 destructible by water, and which disappears spon- 

 taneously after the lapse of a few days. A close 

 examination of the reaction has led the author to 

 conclude that the condition for its production is 



