158 THE 3IICR0SC0PE. Oct. 



afterward obtained free from water and found to be a definite 

 chemical compound of hydrogen and oxygen, and dififering from 

 water in containing twice as much oxygen. In this state it is a 

 lieavy. oily liquid, readily decomposed at ordinary temperatures- 

 but if heated, with explosive violence, being converted into ord, 

 inary water and oxygen gas. When poured into water it sinks, 

 b^ing nearly half again as heavy as that liquid, but is miscible 

 in all proportions with it. It has a somewhat bitter, astringent 

 taste, and is colorless, transparent and without odor. It bleaches 

 the skin, hair, ivory and destroys organic coloring matter, pus 

 and all organisms with which it comes in contact by liberating 

 oxygen gas in a nascent or active state. 



The preparations found in commerce are only solutions of 

 this compound in water, and sold in different degrees of concen- 

 tration or strength, rated by the number of volumes of oxygen 

 gas they can l)e made to yield. A fifteen volume solution is 

 one that will give off fifteen volumes of gas from one volume of 

 the solution. A ten volume solution will yield ten pints of 

 0X3^gen gas frora one pint of tlie solution, and so on. 



These solutions, although more stable than mere concentrated 

 preparations, nevertheless decompose and lose their nascent 

 oxygen on which its powerful antiseptic powers depend, and 

 consequently we find the commercial brands varying consider- 

 ably from their reputed strengths. The solution containing the 

 ♦greatest percentage of available oxygen is the preparation known 

 as Marchand's, which, when perfectly fresh, is about a fifteen 

 volume solution. 



RECENT PUBLICATIONS. 



The study of the Biology of Ferns by the Collodion Method. By 

 G. F. Atkinson. 8° pp 134, New York, Macmillan & Co, 

 Price 82.25. 



To microscopists this book is of more interest than the or- 

 dinary treatise upon biology on account of its technique. It is 

 especially to be recommended to microscopists because the au- 

 thor is in thorough sympathy with us in all of our purposes. 



He is a teacher and a skilled microscopist, in every manner 

 qualified to write on such a topic. His book contains a record 

 of his own work and discoveries. 



