AGRICULTURAL CHEMISTEY — AGROTECHNY. 615 



distillate being oxidized and redistilled as has just been described. The use 

 of the relatively large quantity of chromic acid indicated is found to increase 

 the delicacy of the reaction. By the proposed method it is very easy to detect 

 one part of methyl alcohol in 100,000 parts of water, and by making one pre- 

 liminary distillation to concentrate the methyl alcohol, collecting the first 100 cc. 

 from a liter and then proceeding as before described, a very strong test was 

 obtained from a solution containing only one part of methyl alcohol per million. 



" When testing for methyl alcohol in the presence of strong ethyl alcohol it is 

 advisable to dilute the alcohol with water to obtain approximately a 20 per 

 cent solution, as otherwise the action of the chromic acid on the ethyl alcohol 

 may become explosively violent." 



With the modified method it is possible to detect 0.1 per cent of methyl alcohol 

 in 80 per cent ethyl alcohol, and with fractionation 0.01 per cent. 



As formic acid is becoming' of importance in regard to food products, the 

 author studied Us reduction with various substances, particularly as regards 

 sensitiveness. The substances tried for this purpose were magnesium filings, 

 metallic calcium, coppere<l zinc filings, coppered zinc dust, zinc amalgam, cop- 

 pered aluminum, 1 per cent sodium amalgam, 1 per cent sodium amalgam with 

 magnesium chlorid solution, aluminum, aluminum amalgam, zinc dust, and zinc 

 filings. With a 1 per cent solution of formic acid the first 4 substances gave a 

 positive reduction, the 5 following a negative result, and the 3 last only faint 

 evidences of retluction. With 0.1 per cent solution of formic acid the first 4 

 substances mentioned gave a positive reduction. All things considered, mag- 

 nesium filings seemed to give the best results, and form the basis of a qualita- 

 tive method which is given. 



The qunntltative estimation of formic acid is accomplished as follows: "Dis- 

 till the solution containing the formic acid with a small quantity of phosphoric 

 acid until the distillate is no longer acid. If the volume of this distillate is too 

 large to be conveniently handled, neutralize it with sodium hydroxid and evapo- 

 rate to a convenient volume. Add an excess of platinic chlorid and suflicient 

 acetic acid to make the solution strongly acid (usually about 1 or 2 cc. of glacial 

 acetic acid for less than 1 gm. of formic acid), and boil the solution for 1 hour, 

 using a refiux condenser. Collect the reduced platinum in the usual manner 

 and weigh. The weight of the platinum multiplied by 0.472 equals the formic 

 acid present." 



The possibility of using the electrical conductivity method for this purpose is 

 suggested. 



In regard to Halphen's reaction, L. Rosenthaler {ZtscJir. JJrttersuch. 'Nahr. 

 u. Oenussmtl., 20 {1910), Xo. 7, pp. JfoS, //o'/). — The author determined the 

 effect on the reaction (E. S. R., 10, p. 315) of substituting various other sub- 

 stances for amyl alcohol. 



Positive results were obtained with methyl, ethyl, propyl, isobutyl, allyl, and 

 benzylic alcohols, santalol, and amylene hydrate. With allyl alcohol the 

 coloration obtained was orange, and with ethylene glycol after I hour faintly 

 red, becoming more intense 5 minutes later. With glycerin the reaction ap- 

 peared only after J hour. When no alcohol at all was employed a faint red 

 coloration was obtained after f hour, which later became much more intense. 



The determination of arsenic in insecticides, E. B. Holland {Jour. Indus, 

 and Engin. Chem., 3 {1911), A'o. 3. pp. 168-171).— This is a study of methods. 



The author at first adopted Thatcher's suggestion for determining arsenious 

 acid with the Mohr method, with particular regard to the ratio of the sample to 

 be taken to the acetate solution (1:25). This was, however, found to be too 

 small, and it was further noted that the practice of adding hydrochloric acid to 



