Chemistry and Physics. 79 



profitably under the present condition of prices, but the produc- 

 tion of nitrites from ammonia, by oxidizing it with air or oxygen 

 in the presence of pyrites under certain conditions, according to a 

 patented process of Bayer & Co., seems to be more promising. — 

 Derichte, xxxix, 1366. h. l. w. 



3. The Detection and Determination of /Small Quantities of 

 Iron. — A. Mounetrat has found that the green color produced 

 by passing hydrogen sulphide gas for about ten minutes through 

 dilute, slightly ammoniacal solutions of iron salts is a much more 

 delicate test than the familiar sulphocyanide reaction. It appears 

 that the ferrous sulphide forms a colloidal solution when very 

 little of it is present. The green color is discharged by concen- 

 trated solutions of ammonium and sodium sulphates and of 

 sodium chloride, but many organic substances such as glycerine, 

 sugars, tartrates, etc., increase the stability of the solutions and 

 make it possible to obtain stronger ones. The limit of the deli- 

 cacy of the reaction is about one part of iron in a million, when 

 it is carried out in the manner just described, but the delicacy 

 can be made greater by adding i'our or five milligrams of albu- 

 men to the ammoniacal solution, saturating with hydrogen sul- 

 phide as usual, then mixing with an equal volume of alcohol and 

 allowing the liquid to stand ten or twelve hours. A green film 

 is then found at the bottom of the vessel, due to the precipitation ' 

 of a part of the albumen. It is stated that small quantities of 

 mercury, lead, silver, chromium, nickel do not interfere with the 

 reaction, although copper does so. The green colors obtained 

 with amounts of iron varying from y^Vo to xto o"o"o o" are practically 

 proportional to the amounts, so that it is possible to make quanti- 

 tative determinations in this way. — Comptes Bendus, cxlii, 1049. 



h. l. w. 



4. Quantitative Determination of Acetone. — Adolph Jolles 

 has devised a method for this purpose, which depends upon the 

 combination of sodium bisulphite with acetone according to the 

 equation 



(CH,),CO + NaHSO,= (CH 3 ) a C<^ a . 



A titrated solution of bisulphite is added in such quantity that 

 three or four times the required amount is present, and after 

 standing 30 hours it is titrated back with iodine solution. Each 

 molecule of bisulphite corresponds to a molecule of acetone. The 

 reaction takes place slowly, and it was not found possible to 

 shorten the time of standing. Test analyses gave very accurate 

 results. They were made by mixing 25 cc of liquid containing 

 about 0-05 s of acetone with 25 cc of \ normal bisulphite in a stop- 

 pered flask, then, after 30 hours, titrating back with y L normal 

 iodine solution. —Berichte, xxxix, 1306. h. l. w. 



5. Avogadro and Dalton ; the Standing in Chemistry of their 

 Hypotheses ; by Andrew N. Meldrum ; 8vo, pp. 113. Edin- 

 burgh, 1906 (James Thin). — This is a very interesting essay deal- 

 ing chiefly with the relative importance of the atomic and molecu- 



