ODOROUS BODIES. 385 



if volatile, as peroxide of hydrogen, produce a peculiar odor, but not 

 if they are fixed, like the peroxides of barium and manganese. Ozone, 

 whether it be a polarized condition of oxygen, of oxygen combined 

 with itself, or in some other state, possesses a very remarkable pun- 

 gent odor. It is remarkable, that hydrogen, the lightest and most 

 diffusible element with which we are acquainted, produces, when in 

 combination with all other elements, excepting oxygen, the most pow- 

 erful odorous bodies with which we are familiar. Thus, with nitrogen, 

 it forms the pungent substance, ammonia ; with chlorine, hydrochloric 

 acid ; with cyanogen, a hypothetical radical composed of carbon and 

 nitrogen, both of which are inodorous, hydrocyanic acid ; with carbon 

 only, the carburetted hydrogens (coal-gas, and marsh-gas) ; with 

 phosphorus, phosphuretted hydrogen ; and with sulphur, sulphuretted 

 hydrogen. All these compounds are relatively unstable, and prone 

 to oxidation. With oxygen in equal proportions, hydrogen forms the 

 inodorous, though volatilizable body, water. 



Although, then, neither the physical nor the chemical conditions of 

 matter, which are distinctive of odorous bodies, can be clearly defined, 

 volatility\on the one hand, and a condition of chemical instability, 

 especially that of imperfect oxidation, on the other hand, are probably 

 the two most general characteristics of odorous bodies. 



If the cause of odor generally is but little known, still less are the 

 qualitative characters of different odorous bodies, and the causes of the 

 varieties of smell, understood. In this part of the inquiry we are met 

 with singular perplexities and contradictions ; thus, bodies differing 

 much in nature, have similar kinds of odor ; as, for example, garlic 

 and the vapor of arsenic, as this becomes changed into arsenious acid ; 

 phosphorus, also, has a garlicky smell. At present all attempts to 

 classify odors are futile. The quantitative power, or intensity of odor, 

 in certain bodies, is very remarkable. It is very intense, and capable 

 of propagation to great distances, in the case of camphor, turpentine, 

 ether, and musk ; whilst, on the other hand, it is feeble, and acts only 

 at short distances, in the case of caoutchouc, gum, or sugar, the odors 

 of which latter substances may be due even to associated aromatic 

 impurities. 



The extreme divisibility and minuteness of the ultimate odorous 

 particles, is evidenced in such facts, as that a drop of ether will im- 

 pregnate the atmosphere of a large apartment, and that a grain of 

 musk has been kept for ten years, emitting constant odor, without, it 

 is said, suffering any appreciable loss of weight. This fact has been 

 quoted in support of an idea, that odors are not caused by material 

 emanations from the odorous substance, but perhaps by subtle motions, 

 or undulations, of a peculiar kind, originating in the odorous bodies 

 themselves, and exciting similar undulations in the atmosphere, or in 

 some special medium, which, impinging on the olfactory nerves, pro- 

 duce the sensation of smell. But for such an experiment to be con- 

 clusive, the hydrornetric condition of the musk, at the commencement 

 and end of so long a trial, should be accurately determined, otherwise 

 it becomes quite valueless, even though other many obvious causes of 

 fallacy be eliminated. Moreover, strongly odorous bodies, such as 



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