BUNSEN ON THE CACODYL SERIES. 297 
The cyanide of cacodyl thus obtained, forms at 33° C. an 
zthereal colourless liquid, which is strongly refractive, and at 
32:5° C.* becomes a mass of large crystals of a diamond lustre, 
which are similar to frozen moisture on the surface of glass, and 
do not differ much from arsenic acid in appearance. This sub- 
stance has a great tendency to crystallization, and is deposited 
in extraordinary large crystals by slowly cooling the liquid which 
comes off from the first crystallization. The crystals may how- 
ever be obtained much more beautiful, by allowing the substance 
to sublime at the ordinary temperature and deposit itself on a 
glass tube moistened with water. They sometimes attain a 
length of four or five lines in this way. The form is a slightly ob- 
lique four-sided prism, the edges of the smaller sides being trun- 
cated. It was impossible to make any accurate measurement of 
the angles, in consequence of the volatility of this poisonous 
compound. This substance appeared to boil at a temperature 
somewhere about 140° C. It inflames when heated in the open 
air, and burns with a reddish blue flame, emitting a strong 
smoke of arsenious acid. It is slightly soluble in water, but 
very soluble in ether and alcohol. It appears to be the most 
poisonous of all the cacodyl compounds. It produces a sudden 
cessation of muscular power in the hands and feet, giddiness and 
insensibility, which ends in total unconsciousness. ‘These effects 
do not however last long, provided the person is not long ex- 
posed to the action of its fumes. 
__ A solution of silver is precipitated as cyanide of silver: nitrate 
of the protoxide of mercury is reduced, but no effect is produced 
ina solution of the nitrate of the peroxide. Chloride of mercury is 
immediately precipitated in combination with the oxide of cacodyl. 
A solution of this substance mixed with salts of the two oxides 
of iron, precipitated by potash, and heated with acetic acid to re- 
dissolve the hydrated precipitate, did not produce any prussian 
blue; but on adding a stronger acid as the solvent it was imme- 
diately formed. Weak acids do not decompose it, but the 
stronger acids act in precisely the same way as with the other 
soluble cyanides. 
_ The carbon and hydrogen were easily determined by the usual 
* In determining the melting point of this substance I employed a very con- 
venient and safe method, which might be applicable in many other cases. A 
very thin glass tube is partly filled with the substance and closed at both ends. 
| This is immersed in water heated to different degrees of temperature, and it is 
thus very easy to determine the melting point with great accuracy. 
VOL. III. PART X. x 
