42 M. Thenard on the [Jan. 



oxide, and there result muriate of barytes, and weakly oxygen- 

 ated water. The sulphuric acid precipitates the barytes, and 

 liberates the muriatic acid, which then acts upon afresh quantity 

 of peroxide of barium, so that there is no difficulty in repeating 

 the process several times, and there remains at length water 

 holdmg more or less oxygen in solution. The mode in which 

 the sulphate of silver acts is evident, the use of it is to separate 

 the muriatic acid, and replace it by sulphuric ; the barytes com- 

 bines with the sulphuric acid, and precipitates it. When the 

 operation is performed with pure materials, and in proper pro- 

 portions, it is evident that thfe last result is entirely oxygenated 

 water : it is then to be put into a glass vessel with a foot, and 

 this placed in a large capsule, two-thirds filled with concentrated 

 sulphuric acid, the apparatus is to be put under the receiver of 

 an air-pump, and the air exhausted. The pure water evaporates 

 much more readily than the oxygenated water, so that in two 

 days it will probably contain 250 times its volume of oxygen; 

 and when the solution contains 475 times its volume of oxygen 

 at the temperature of 57°, no further concentration takes place 

 by keeping it longer in vacuo.* 



Physical Properties of the Peroxide of Hydrogen, 



The peroxide of hydrogen is fluid and colourless as water. It 

 is inodorous, or at least it is so nearly so, that few persons can 

 discover any smell. It gradually destroys the colour of litmus 

 and turmeric paper, and makes them quite white. It acts upon 

 the epidermis very readily, sometimes suddenly, whitens it, and 

 occasions prickings, which continue for a longer or shorter 

 period, according to the nature of the individual and the thick- 

 ness of the portion of liquor applied ; if it be too thick or be 

 renewed, the skin itself is attacked and destroyed. Applied to 

 the tongue, it whitens and pricks it, thickens the saliva, and 

 produces a sensation which it is difficult to describe, but which 

 resembles that of certain metallic solutions. Its tension is 

 extremely weak, much weaker than that of water : this is the 

 reason why oxygenated water, at common temperatures, is con- 

 centrated in vacuo by the intervention of an absorbing body 

 such as sulphuric acicf. This also is the reason why the evapo- 

 ration in this case becomes gradually slower, so that at the end 

 it is extremely slow; still, however, it always takes place, 

 for it finishes by the whole of the hquor disappearing ; and this 

 occurs without the production of any gas, which shows that the 

 peroxide of hydrogen is vaporized without decomposition. 



I tried, but ineffectually, to solidify the peroxide of hydrogen. 

 Exposed to a low temperature for three quarters of an hour, it 

 remained liquid ; when also water which contains only 30 or 40 



* For the precautions requisite to be observed in preparing oxygenated water, the 

 reader is referred to 31. Thenard's Traits de Chimie, torn. i. p. 563. 



