190 ANNUAL OF SCIENTIFIC DISCOVERY. 



EFFLORESCENCE AND HYDRATION. 



According to M. Debray, a hydrated salt has for each tempera- 

 ture a tension of dissociation which is measured by the elastic force 

 of the aqueous vapor which it emits at this temperature. There- 

 fore, a salt effloresces when the tension of its watery rapor is 

 greater than that of the aqueous vapor existing in the atmosphere. 

 A dry salt becomes hydrated when the tension of the aqueous 

 vapor contained in the atmosphere is greater than that which the 

 salt emits at the same temperature. Hydrous salts which do not 

 effloresce owe this property to the fact that the tension of the 

 aqueous vapor emitted by them at ordinary temperatures is al- 

 ways inferior to that commonly possessed by the watery vapor of 

 the atmosphere ; they effloresce when placed in an atmosphere 

 where the elastic force of the aqueous vapor contained in the air 

 is less than that which they emit. — Comptes Bendus. 



THE MONOCARBON SERIES OF COMPOUNDS. 



The modern chemist is able to separate organic carbon com- 

 pounds into divisions which greatly simplify his science, — always 

 recognizing as preliminary facts : first, that every body of the or- 

 ganic type is built upon the element carbon ; and second, that this 

 element possesses the property of combining with itself, by which 

 property it is enabled by the combinations it makes with other 

 elements, to produce distinct series of compounds, which are 

 classified, in accordance with this rule, into monocarbons, dicar- 

 bons, and so on. 



In illustration may be given the names of the first five series ; — 



The Methyl series : in this the carbon stand as 1 — C. 



The Ethyl series : •' " "^ 2— Cg- 



The Propyl series : *' ". *♦ 3— C3. 



The Butyl series : " « *♦ 4— C4. 



The Amyl series : '' " ** 6— C5. 



and so on up to the Melisyl series, where the carbon stands Coo- 



Every one of these groups, as well as the higher ones, possesses 

 an analogous compound called an alcohol. We have methylic 

 alcohol, wood spirit or naphtha ; ethylic alcohol, ordinary alco- 

 hol; propylic and butylic alcohols; and amylic alcohol, fusel oil 

 or potato spirit. The difference of the carbon may be siiown by 

 burning them in spirit lamps : the methylic lamp burns with little 

 light and no smoke, not blackening a white plate ; the ethjiic 

 lamp 5'ields a faint trace of darkness of unconsumed carbon ; the 

 propylic and butylic lamps have cloudier flames and yield much 

 deposit; while the amylic lamp burns dull and heavy, its light 

 peering through smoke, and yielding enough unconsumed carbon 

 to cover the plate in a few seconds. 



In combining with other elementary bodies to produce the 

 groups of the monocarbon series, the carbon forms first a union 

 with hj'drogcn, producing a new and basic substance called a radi- 



