500 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



and i^lace them in an alkaline color bath. 3 B, XXXVI., 

 374. 



Schweitzer's solvent for cellulose. 



Professor C. Neubauer recommends the following method 

 for obtaining the well-known cupro-ammonium solution for 

 technical use. He prepares an oxide of copper by the precip- 

 itation of sulphate of copper solution with caustic soda, in 

 presence of sal ammoniac. The resulting precipitate is thor- 

 oughly washed with water, first by decantation and then upon 

 a filter, after which it is preserved under w^ater. To prepare 

 the cupro-ammonium solution the oxide above referred to, 

 after thorougli agitation with the water, is slowly added to 

 a quantity of ammonia contained in another vessel. The ad- 

 dition of oxide is to be continued so lonsj as the same is dis- 

 solved by the ammonia. The resulting deep-blue colored 

 solution dissolves cotton-wool at once, and in considerable 

 quantity. Fresenius' Zeit. fiXr Anal, Chem.^XlY., 195. 



OLEIC ACID AS A SOLVENT AND TEST FOR GUM COPAL. 



Avery small quantity of oleic acid dropped upon a sample 

 of gum copal, and but gently warmed, will dissolve that gum 

 completely. It is also an excellent reagent for distinguish- 

 ing true amber from its imitation in copal. 9 (7, XIII., 

 25. 



ADULTERATION OF BEESWAX WITH PARAFFIN. 



To detect this very common form of adulteration. Miller 

 recommends that a small quantity of the suspected substance 

 be tested to about 325 Fahr. with concentrated sulphuric 

 acid, and upon cooling, the paraffin, if it be present, will be 

 found upon the surface of the mixture. Fresenius' Zeit. fur 

 Anal Chem.^ XIV., 200. 



BLEACHED ISINGLASS. 



On account of the preference shown by consumers gener- 

 ally for thin white isinglass, the inferior dark and bloody 

 samples are bleached chemically at St. Petersburg, and sold as 

 of first quality, although they have naturally a yellowish cast. 

 According to Kattus, it has been established by experience 

 that the bleaching impairs its adhesiveness and clarifying 



