152 THE ALUMNI JOURNAL 



PROPERTIES. 



Peroxide of Hydrogen in a pure state is a thick, colorless liquid 

 having a specific gravity of [.499, and hoils at 69 degrees under a 

 pressure of 20 millimeters. It has a color much darker than the blue 

 color of water. It is reasonably stable at an ordinary temperature, 

 but when heated to 60 degrees or over it explodes with considerable 

 violence. Impurities decompose it rapidly. It oxidizes organic matter 

 with such rapidity that the reaction is often accompanied by a flame. 

 Particles of dust, metals in a finely sub-divided state decompose it 

 with extreme violence. At a low temperature crystals of pure peroxide 

 are formed. By freezing much of the water may be separated from 

 the peroxide ; by distilling in vacuo solutions may be increased in 

 strength to as much as 100 per cent. A well known 25 per cent, 

 solution is made by distillation and admixture with ether. Distillation 

 of peroxide is an extremely hazardous undertaking and should be 

 conducted with great caution. The presence of the faintest trace of 

 foreign matter may cause an explosion ; the whole breaking up into 

 oxygen gas and water. Loss of life and limb mark the attempts that 

 have been made in the past to perform this operation. The ordinary 

 3 per cent, solution of the market, however, may be made with com- 

 parative safety, providing its generation is not attempted in a closed 

 vessel. The aqueous solution contains a certain percentage of free 

 acid usually sulphuric, and possibly various preservatives such as 

 acetanilid, boric acid, salicylic acid, sodium salicylate, alcohol, glycerine, 

 caffeine, sodium benzoate, salol. benzoic acid, boroglyceride. sodium 

 chloride, etc. 



Some manufacturers keep the solution strongly acid throughout the 

 process and at the end neutralize the acidity with barium hydrate, but 

 the most careful manipulators bring the product to a neutral and 

 slightly alkaline point with barium dioxide at the end, the latter process 

 being considered the best, and producing the most satisfactory results. 

 Peroxide changes odor and flavor of most viatile oils. Those which 

 are not affected are: Oil of eucalyptus, oils of pine, oil of star aniseel ; 

 anehtol, oil of aniseed, borynlacetate, eucalyptol, thymol. 



METHODS OF CLARIFVING. 



( hi a large scale the best method is by settling. If left undisturbed 

 in large vats for four or five days the precipitate, usually of barium 

 >ulphate, will settle to the bottom of the tank and the clean solution 

 may be syphoned off. Another method is by pressure filtration with a 

 filter press made of wooden frames. Gravity filtration through filter 



