Properties. - When the watery solution thus obtained is evaporated it forms a transparent oily liquid; but it is generally employed in the form of a 3 per cent. solution (10 to 15 volumes) in water or in ether. The ethereal solution is commonly known by the name of ozonic ether; it is generally more stable than the aqueous solution, which, especially if kept in a badly stoppered bottle, soon decomposes into water and oxygen.

Preparation. - It is generally prepared by treating barium di-oxide with dilute sulphuric acid (BaO2 + H2 SO4 = H2O.2 + BaSO4) and filtering off the aqueous solution from the sulphate of barium which is precipitated.

Action and Uses. - Peroxide of hydrogen has a powerful oxidising effect upon organic substances, readily giving off an atom of oxygen in much the same way as ozone. It has therefore been used for similar purposes to ozone. It destroys bacteria, and is a powerful antiseptic.1 When mixed with the secretion from a chancre it destroys its infective power; and it has been employed as a local dressing for chancres, and also as an application for diphtheritic sore-throat. Curiously enough, although when mixed with blood or with albumen it becomes decomposed almost immediately, it appears to be tolerably stable in the body, and is said to have been found in the urine after it has been taken by the mouth. By long-continued action upon egg-albumin, it is said to produce hemi-albumose and peptone.2 Its internal administration has been recommended in rheumatism, scrofula, diabetes, and cardiac disease.

1 Professor Dewar, Cambridge, unpublished experiments.

2 Chandelon, Beitrag zum Studium der Peptonisation, Ber. d. Deutsch. Chem. Ges. XVII. p. 2143 (1885).