and the Sulphurets of Kakodyl. 183 
respect surpasses even the succinic acid. Concentrated nitric 
acid, even nitromuriatic acid, or indeed a mixture of the chro- 
mic and sulphuric acids, exerts no action upon it even at a boil- 
ing temperature : if the excess of the first-named acid be driven 
off by evaporation, a thick syrupy liquid remains, which is 
probably NO°+C* H® As? O%, which can bear a higher tem- 
perature than NO® without being decomposed, and when 
heated still more strongly burns with a slight explosion. 
That, however, which renders this body so very interesting 
for the theory, is the great facility with which its reduction 
may be effected; phosphorous acid abstracts 2 atoms of 
oxygen and produces the oxide. Protochloride of tin acts in 
the same way, except that the chloride of the radical is formed ; 
but what appears to me still more remarkable is, that this re- 
duction may be effected by means of metallic zinc, kakodylate 
of zine being formed. 
This acid is very weak; it certainly does decompose the 
carbonates, but only with slowness and difficulty. Its salts 
are all soluble in water, and may be crystallized from alco- 
hol. Oxide of silver forms three salts; the neutral one, which 
crystallizes from its alcoholic solution in long fine silky 
needles, is obtained by dissolving pure oxide of silver in ka- 
kodylic acid; the salt is not changed in the air unless light is 
admitted; when heated red-hot it leaves metallic silver per- 
fectly free from arsenic. It is anhydrous, and has the formula 
C*H® As?O0?+ Ag O. 
By treating an aqueous solution of kakodylic acid with car- 
bonate of silver, another salt somewhat similar in appearance 
to the above is obtained. It is a ter-acid salt, and is formed 
because the terkakodylate of silver cannot further decompose 
the carbonate. The formula is 3 (C4 H® As? O%) + Ag O. 
The third compound is a double salt of kakodylate and ni- 
trate of silver. It is obtained by mixing together alcoholic 
solutions of kakodylic acid and nitrate of silver ; its formation 
is accompanied by a very remarkable phenomenon. First of 
all the neutral salt is separated in the form of silky needles, 
which in a few moments change into silky scales while still 
under the liquid. This salt blackens with great rapidity in 
the air, and explodes when heated. Its composition is 
Ag O, NO* + Ag O, C* H® As? O%. 
The salt of mercury only crystallizes when an excess of 
kakodylic acid is present: it forms exceedingly fine silky 
needles, which aggregate in star-shaped masses. It is decom~ 
posed by water, oxide of mercury being separated. The potassa 
salt is soluble in water, but not in absolute alcohol and eether. 
It crystallizes in concentric radiated groups of crystals like 
