the compounds of chromium. 911 
coloured liquid. This process lasts about ten minutes, or a 
quarter of an hour, when the evolution of the red fumes 
suddenly stops. The matter in the retort has now assumed 
a fine green colour. If the distillation be continued, a liquid 
passes into the receiver, consisting chiefly of acidulous water, 
and destroys the red liquid. The process therefore must be 
stopped as soon as the evolution of red fumes is at an end. 
The quantity of red liquid obtained from the above stated 
proportions of materials is about 200 grains ; but it varies 
somewhat with the care with which the process is conducted. 
The quantity of protoxide of chromium remaining in the 
retort is also various. With the above proportions it usually 
amounts to 27-3 grains, equivalent to S 6'5 grains of chromic 
acid, or T 3 T ths of the whole chromic acid in the salt ; but it 
varies with the quantity of common salt employed. If we 
introduce only a portion of the common salt at first, and add 
the rest at intervals, till the matter in the retort has assumed 
a green colour, the protoxide -of chromium remaining in the 
retort is a maximum, and the quantity of red liquor obtained 
a minimum. When the atoms of chlorine in the common 
salt are to those of chromic acid in the bichromate as 3 to 2, 
the product of red liquor is greatest. We may vary the 
sulphuric acid considerably, but the process is easiest when 
the quantity of acid used is sufficient to convert the salt into 
a semifluid magma. Chromate of lead or chromate of potash 
may be substituted for bichromate of potash. 
The red liquid possesses the following properties : its 
colour is a deep, but lovely crimson ; so intense indeed as 
to render the liquid opaque, except in very thin films. 
Its taste is sweetish, astringent, and acid. 
