478 CONSIDERATION OF CARBON COMPOUNDS. 



12.5 C. The compressed liquid is sold in tubes, from which it is permit- 

 ted to escape through a small opening when used as a local anaesthetic. 

 It is highly inflammable. It is known also as kelene or chelene. 



Ethyl bromide, C 2 H 5 Br (Brom-ethane, Hydrobromlc ether], is obtained by 

 the same reactions as ethyl chloride, substituting bromine for chlorine. It is 

 a colorless, heavy, volatile liquid. Specific gravity 1.473; B. P. 40 C. When 

 inhaled it rapidly produces anaesthesia, followed by quick recovery. 



Somnoform is said to be a mixture of 60 parts of ethyl chloride, 35 parts of 

 methyl chloride, and 5 parts of ethyl bromide. It is used to some extent in 

 dentistry as an anaesthetic. 



Ethyl iodide, C 2 H 5 I, may be obtained similarly to the chlorine or bromine 

 compound. It is a colorless liquid with the boiling-point of 72 C. 



Compounds of hydrocarbon (alkyl) radicals with other elements. Some 

 metals, as zinc, magnesium, cadmium, aluminum, etc., can form compounds 

 with alkyl radicals; for example, Zn(CH 3 ) 2 , Sn(C 2 H 5 ) 4 . Likewise, alkyl rad- 

 icals can be substituted for one or more atoms of hydrogen in ammonia (NH 3 ), 

 arsine (AsH 3 ), and phosphine (PH 3 ) ; for example, NH. 2 .CH 3 , AsH(CH 3 ) 2 , 

 P(CH 3 ) 3 . The alkyl derivatives of ammonia are treated in chapter 49. One 

 of the arsenic compounds possesses some interest because of its use in med- 

 icine, although its employment is limited. When arsenous oxide and potas- 

 sium acetate are distilled together, a heavy, horribly-smelling, poisonous, 

 fuming oil is formed, the principal constituent of which has the composition, 

 [(CH 3 ) 2 As] 2 O. The reaction is, As 2 O 3 + 4CH 3 COQK = K 2 C0 3 + 2CO 2 + 

 [(CH 3 ) 2 As] 2 O. Dimethyl arsine oxide is known best as cacodyl oxide, the 

 word cacodyl having been adopted in allusion to the disgusting odor of the 

 compound. It contains the univalent radical, (CH 3 ) 2 As , which acts like an 

 atom of a univalent metal. Cacodyl itself, (CH 3 ) 2 As As(CH 3 ) 2 , also exists. 

 The oxide has a strong affinity for oxygen, and inflames in oxygen gas, but not 

 in air. By oxidizing cacodyl oxide with mercuric oxide, cacodylic acid is formed, 

 (CH 3 ) 2 AsO.OH, which yields odorless prisms, easily soluble in water. Sodium 

 cacodylate, (CH 3 ) 2 AsO.ONa -f 3H 2 O, also called sodium dimethyl arsenate, is 

 evidently closely related to mono-sodium arsenate. It is a white odorless 

 powder, very soluble in water, forming needle-shaped crystals, which are hygro- 

 scopic, but otherwise very stable. The aqueous solution is alkaline to litmus, 

 but nearly neutral to phenolphthalein. Its action is similar to that of other 

 arsenic compounds, but it is said to be much less toxic, and also less apt to 

 cause undesirable side-effects. 



QUESTIONS. How do hydrocarbons occur in nature, and by what processes 

 are they formed in nature or artificially? State the general physical and 

 chemical properties of hydrocarbons. State the composition and properties 

 of methane, and also the conditions under which it is formed in nature. What 

 is coal, what are its constituents, from what is it derived, and by what process 

 has it been formed ? What is crude coal-oil, what is petroleurn-benzin, and wh at 

 is petrolatum? How is illuminating gas manufactured, and what are its chief 

 constituents? Mention some of the important substances found in coal-tar. 

 State of chloroform : composition, properties, two processes for its manufacture, 

 and method of detection. Explain the action of chlorine on methane and 

 name the products. How is iodoform made and what are its properties ? 



