Very important distinctions-those of caking or non-caking-are founded on the behaviour of coals when subjected to the process of coking.
Dragged into Stubb's boat with blood-shot, blinded eyes, the white brine caking in his wrinkles; the long tension of Ahab's bodily strength did crack, and helplessly he yielded to his body's doom: for a time, lying all crushed in the bottom of Stubb's boat, like one trodden under foot of herds of elephants.
The property of caking or yielding a coherent coke is usually absent, and the ash is often very high.
An anthracite occurring in connexion with the old volcanic rocks of Arthur's Seat,Edinburgh, which contains a large amount of sulphur in proportion to the Caking coals.
For efficiency the operation must be conducted with small quantities; caking may be prevented by mixing the substance with sand or powdered pumice, or, better, with iron filings, which also renders the decomposition more regular by increasing the conductivity of the mass.
This arrangement has the effect that the salts, as they separate out, slide down the sloping part and arrive in the central channel, which is not exposed to the fire-gases, so that they quietly settle there, without caking to the pan, until they are fished out by means of perforated ladles.