CHEMICAL SCIENCE. 223 



material, of suitable dimensions, should have two rods or sticks sewn 

 to opposite edges. These sticks will hang over the sides of the vessel, 

 and permit the prints to be withdrawn or moved without any risk of 

 injury, and they should remain in soak with warm or cold water for 

 twelve or twenty-four hours. When the prints no longer discolor 

 the water on being agitated, the fluid should be withdrawn, and 

 enough clean water added to cover them. Half a pound of chloride 

 of lime should be made into a paste with cold water, and stirred up 

 with two quarts of water, and allowed to settle for six hours. Part 

 of the clear solution should be added to the bath till the smell of 

 cholerine is perceived, and the prints should be moved to facilitate the 

 action. In very bad cases, one ounce of muriatic acid mixed with 

 a pint of water may be added, and when the bleaching is effected 

 the prints should be well washed with fresh water and slowly dried. 



On the first trial of this process, remarks Dr. Hayes, a degree of 

 alarm will be felt in the case of a highly-prized favorite at this seem- 

 ing careless treatment; but it must be borne in mind that paper 

 is a firmly felted mass of short fibres which may be soaked in various 

 fluids for weeks, and resist all diluted acids and most chemical agents 



* 25 



for a long time wet, if not exposed to mechanical abrasion by touch or 

 rapid motion. 



NEW THEORY OF ODORS. 



A physical theory of odors and savors has been put forth by M. 

 Nickles, who has sought to establish some general laws which preside 

 over the generation and perception of these two properties of bodies. 

 He attributes the formation of odors to three categories. 1. The 

 combination of two inodorous bodies. 2. The action of an odorous 

 on an inodorous body, and reciprocally ; and, 3. The combination of 

 two odorous bodies, which produce either an odor like one of the ele- 

 ments, or an odor entirely new. As examples of the last he cites 

 butyric and ether with the odor of ananas, the essence of apples, 

 and the essence of Gaulteria. M. Nickles finds that there are 

 bodies endowed with a peculiar odor which persists and rules in a 

 great number of combinations, in the same manner as the color or 

 taste of certain bodies is maintained in certain combinations. Two 

 bodies perform an important part in the theory of odors. Hydrogen 

 develops the odor of the bodies with which it combines, and, at the 

 same time, renders them more volatile. Oxygen, on the contrary, 

 diminishes the volatility and odorability of the compounds. Yet 

 oxygen is indispensable to the perception of odors. It seems always 

 to intervene in that act, and perfumes make an impression on the 

 olfactory nerves only in proportion as they are burnt by the air 

 of the atmosphere. Hydrogen and oxygen are inodorous in the 

 pure state. Their compound, water, has an odor, which may be per- 

 ceived when drawing it into the nostrils. In general, the odor and 

 taste of other compounds take from the electro-positive element, 

 which may be a compound radical. There are very few exceptions 

 to this remarkable law. As to savors in particular, M. Nicklds attrib- 

 utes them to catalytic action, or the effects of contact. 

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