A Manual of the Chemistry of the Carbon Compounds

70 TUB WBfflSTRY OF
a salt wbiob is also oontained in the original substance after being
coloured yellow by long exposure to the air. Free croconic acid
C6H6H8 is obtained by adding sulphuric acid and aleohol to the
potassium salt and evaporating the solution; it crystallizes in yellow
lamina). Both rhodizonic and oroconic aoid are oxidized by nitric acid
to kiuonde aoid C6Q0H8, which is tribasio and obtained as a colourless
syrup by adding aloohol to the aqueous solution.
Neither the moleoular weights «or the constitution of these remarkable
compounds are known.
HYDROCARBONS OF THE SERIES C^H^, OR PARAFFINS.
Of the hydrocarbons homologous with marsh-gas those containing
less than five atoms of carbon are gases at the onlinary temperature;
the next higher ones are mobile, colourless liquids, having a faint but
characteristic ethereal odour; and those richest in carbon are crystalline
solids. A mixture of the latter has been known for a long time
under the name of paraffin (parum affinis), a name given to them
from the fact that they resist in the cold the action of strong oxidizing
agents. But as the gaseous and liquid hydrocarbons of this group
show the same resistance against nitric acid, chromic acid, &c, it
appears appropriate to give to the whole group the name the
paraffins. Whilst they ara not acted upon in the cold even by a
mixture of fuming nitrio and sulphuric acids, on the application of
heat they are oxidized, even by dilute nitric acid, the produots consisting
of carbon dioxide and water, besides small quantities of fatty
acids, succinic acid, and uitriles, whilst chromic acid produces carbon
dioxide and water, as well as a little acetic acid.
By acting on the paraffins with chlorine in diffused daylight,
substitution products are formed, the first product being the chloride
of a monad radical, marsh-gas or methane yielding methyl chloride :—
CH4 + Cla » CHgCl + HC1
By continued action of chlorine a further exchange of chlorine for
hydrogen takes place; thus frominarsh-gas the following bodies have
been obtained:—
CH4 +CL=CHSC1 +HC1
CH3C1 + CL = CH2CL + HC1
CH2CL + C12= CHCla + HC1
CH Cls + Cla = CC14 + HOI
In the same way the six atoms of hydrogeu in ethane C2H0 have
been substituted one after the other by chlorine, whilst in propauo
0»Ha and hexane CBH,4 ouly six have thus been replaced.