Chemistry and Physics. 325 



at first by three decantations with boiling water, then with boil- 

 ing water on the filter until the chlorine reaction has disappeared. 

 Dry and weigh it. — Zeitschr. analyt. Chem., xlv, 31. h. l. w. 



2. The Determination of Grape Sugar. — The present methods 

 for the quantitative determination of glucose are not based upon 

 definite chemical equations ; for instance, the amount of cuprous 

 oxide produced by Fehling's method depends upon conditions of 

 concentration, etc. Glassmann has now worked out two modifi- 

 cations of Knapp's method, which appear to depend upon strict 

 stochiometric principles, but only one of these, apparently the 

 most convenient one, will be noticed here. The grape sugar 

 solution is poured into a boiling solution of mercuric cyanide and 

 caustic potash, or a similar alkaline solution of potassium mer- 

 curic iodide, when metallic mercury is precipitated according to 

 the following equations : 



and 



CH 2 OH(CHOH) 4 CHO + 3Hg(CN) 2 + 6KOH = 

 COOH(CHOH) 4 COOH + 4lI 2 + 6KCN + 3Hg, 



CH OH(CHOH) 4 CHO + 3HstT„.2KI + 6KOH=: 

 COOH(CHOH) 4 COOH + 4H 2 + 8KI + 3Hg. 



The precipitate is filtered and washed, dissolved by heating with 

 strong nitric acid, and the mercury is determined with a standard 

 thiocyanate solution, with ferric alum as an indicator, according 

 to the method of Rupp and Krauss, which is carried out exactly 

 like Volhardt's volumetric method for silver. A tenth-normal 

 NH 4 SCN solution is equivalent to -003009s of C„H 19 6 . (The 

 author incorrectly gives this value for l ccra of y^ normal solu- 

 tion.) A number of test analyses carried out with pure grape 

 sugar give very satisfactory results, but no statements are made 

 in regard to substances which interfere with the process. — 

 Berichte, xxxix, 503. h. l. w. 



3. The Soiling of the Metals of the Platinum Group. — 

 Moissan has heated samples of 150§ each of osmium, ruthenium, 

 platinum, palladium, iridium and rhodium, in his electric furnace, 

 and has succeeded in bringing all of them to the point of ebul- 

 lition and distillation by the use of currents of from 500 to 700 

 amperes and 110 volts. Fusion took place in one or two minutes, 

 and boiling was reached in less than four minutes. The vapors 

 were condensed upon a copper tube through which a rapid stream 

 of cold water was passed, so that metallic spherules or micro- 

 scopic crystals, usually in the form of felt, were produced. All 

 of the metals dissolved carbon from the crucible, which they 

 gave up as graphite upon cooling. The most difficult of all the 

 metals to distil is osmium. Palladium is more readily fusible 

 than platinum, but it does not appear to be more readily volatile 

 than platinum and rhodium. — Gomptes Renclus, cxlii, 189. 



h. l. w. 



Am. Jour. Sci.— Fourth Series, Vol. XXI, No. 124.— April, 1906. 

 23 



