Page:EB1911 - Volume 20.djvu/68

 inventors, and even at the present day processes are being patented, having for their object the boiling out of fruits with water or salt solutions, so as to facilitate the separation of the oil from the pulp by gravitation. Naturally these processes can only be applied to those seeds which contain large quantities of fatty matter, such as coconuts and olives. The rendering process is, however, applied on a very large scale to the production of animal oils and fats. Formerly the animal oils and fats were obtained by heating the tissues containing the oils or fats over a free fire, when the cell membranes burst and the liquid fat flowed out. The cave-dweller who first collected the fat dripping off the deer on the roasting spit may well be looked upon as the first manufacturer of tallow. This crude process is now classed amongst the noxious trades, owing to the offensive stench given off, and must be considered as almost extinct in this country. Even on whaling vessels, where up to recently whale oil, seal oil and sperm oil (see Waxes, below) were obtained exclusively by “trying,” i.e. by melting the blubber over a free fire, the process of rendering is fast becoming obsolete, the modern practice being to deliver the blubber in as fresh a state as possible to the “whaling establishments,” where the oil is rendered by methods closely resembling those worked in the enormous rendering establishments (for tallow, lard, bone fat) in the United States and in South America. The method consists essentially in cutting up the fatty matter into small fragments, which are transferred into vessels containing water, wherein the comminuted mass is heated by steam, either under ordinary pressure in open vessels or under higher pressure in digestors. The fat gradually exudes and collects on the top of the water, whilst the membranous matter, “greaves,” falls to the bottom. The fat is then drawn off the aqueous (gluey) layer, and strained through sieves or filters.

The greaves are placed