C. U. C. p. ALUMNI JOURNAL 



219 



of 90% alcohol, and in 9 volumes of 

 70% alcohol, both solutions being slight- 

 ly cloudy. 



A Disinfection Process. 



The process is patented by the 

 Schweizerisches Serum und Impfinstitut, 

 of Bern, Switzerland, and consists of the 

 following : 300 grammes each of anhy- 

 drous copper sulphate, potassium chlo- 

 rate, in fine powder, and pulverized 

 iron are placed in a suitable container, 

 and covered with one liter each of water 

 and formalin. The action of the water 

 [Upon the copper sulphate, resulting in 

 its hydration, generates sufficient heat to 

 decompose the potassium chlorate, and 

 the added heat thus produced is suffi- 

 cient to vaporize the formalin. The 

 liberated oxygen combines with the iron. 

 Manganese dioxide may be added to the 

 other substances. 



Detection of Benzoic Acid in Foods. 



A modification of the so-called Mohler 

 reaction is proposed by J. Grossfeld, in 

 Cheni. Ztg., 1916, as follows: The acid 

 is removed by the aid of ether or other 

 appropriate solvent, and the solution 

 thus obtained is vaporized to dryness at 

 low temperature. The residue obtained 

 is heated on a water-bath for twenty 

 minutes, after adding o.i gramme of 

 potassium nitrate and i mil of concen- 

 trated sulphuric acid. After cooling ?. 

 mils of water are added, the mixture 

 being again heated and subsequently 

 cooled. It is then treated with an exces.s 

 of ammonia water, and mixed with 2 

 mils of a solution made by dissolving 2 

 grammes of hydroxylamine hydrochlo- 

 ride in 100 mils of water. If benzoic 



acid is present a red coloration will be 

 noted. The color reaction is more in- 

 tense if the mixture be warmed and 

 then rapidly cooled. Cinnamic acid pro- 

 duces a similar reaction, but salicylic 

 acid may be readily differentiated. 



Presence of Copper in Formaldehyde. 



H. Kunz-Krause in the Apoteker 

 Zeititng reports that copper contamina- 

 tion of formaldehyde occurs readily, if 

 this has been prepared with aid of a cop- 

 per spiral. Copper formate is produced 

 by the action of formic acid, produced 

 by oxidation of the formaldehyde, on 

 the copper spiral. The presence of cop- 

 per in formaldehyde may be readily de- 

 tected by noting the blue-green colora- 

 tion produced when a few drops of 

 pyridine are added. If copper is pres- 

 ent it can be renovated by treatment 

 with pieces of bright iron. If the alde- 

 hyde has an acid reaction it must first 

 be shaken with calcium carbonate and 

 subsecjuently filtered. 



Determination of Rosin in Gum Resins. 



A method calculated to give approxi- 

 mate results is proposed by Hutin in 

 Caoutchouc et Gutta-Percha, 1916. Ros- 

 in is shown to be present by saponifying 

 I gramme of the gum-resin with the 

 minimum quantity of sodium hydroxide. 

 After dilution with water, a solution of 

 copper sulphate is added in slight ex- 

 cess. If rosin was present it will be 

 shown by the formation of resinate of 

 copper, green in color and soluble in 

 oil of turpentine. In order to approxi- 

 mately determine the quantity of rosin 

 present, the sample to be tested is pow- 

 dered finely and dissolved in 97 to 98 per 



