OILS 435 



imagined that the boiling with litharge effects the separation of the mucilaginous and 

 other foreign matters, -which tend to protect the oils from the action of the oxygen of 

 the atmosphere, and has proposed a process for their separation without the aid of 

 heat. It consists in shaking the oil, previously triturated with litharge, with a 

 solution of the basic acetate of lead for some time, and afterwards allowing the whole 

 to remain still, when the oil separates, and will then dry in twenty-four hours. The 

 solution of acetate of lead which remains may be again used by converting it into the 

 subacetate. A portion of oxide of lead is dissolved by the oil, and when its presence 

 would be prejudicial, it maybe removed by shaking the oil with dilute sulphuric acid. 

 In boiling the oils with acetate of lead and litharge, some painters add about an 

 eighth part of resin, which in that proportion greatly improves the appearance of the 

 paints when dry. 



Before describing these oils separately, it is necessary to show the means used for 

 obtaining them from the seeds, &c. 



PAT OIL MANDFACTUBE. 



Olive Oil. It is the practice of almost all the proprietors in the neighbourhood of Aix, 

 in Provence, to preserve the olives for fifteen days in barns or cellars, till they have 

 undergone a species of fermentation, in order to facilitate the extraction of their oil. 

 If this practice were really prejudicial to the product, as some theorists have said, would 

 not the high reputation and price of the oil of Aix have long ago suffered, and have 

 induced them to change their system of working ? In fact, all depends upon the degree 

 of fermentation excited. They must not be allowed to mould in damp places, to lie 

 in heaps, to soften so as to stick to each other, and discharge a reddish liquor, or to 

 become so hot as to raise a thermometer plunged into the mass up to 96 Fahr. In 

 such a ease they would afford an acrid nauseous oil, fit only for the woollen or soap 

 manufactories. A slight fermentative action, however, is useful towards separating the 

 oil from mucilage. The olives are then crushed under the stones of an edge-mill, and 

 next put into a screw-press, being enclosed in bulrush-mat bags (cabas), laid over 

 each other to the number of eighteen. The oil is run off from the channels of the 

 ground-sill into casks, or into stone cisterns called pizes, two-thirds filled with water. 

 The pressure applied to the cabas should be slowly graduated. 



What comes over first, without heat, is called the virgin oil. The cabas being now 

 removed from the press, their contents are shovelled out, mixed with some boiling 

 water, again put in the bags, and pressed anew. The hot water helps to carry off the 

 oil, which is received in other casks or pizes. The oil ere long accumulates at the 

 surface, and is skimmed off with large flat ladles ; a process which is called lever 

 I'huile. When used fresh, this is a very good article, and quite fit for table use, but 

 is apt to get rancid when kept. The subjacent water retains a good deal of oil by 

 the intervention of the mucilage ; but by long repose in a large general cistern, called 

 I'enfer, it parts with it, and the water is then drawn off from the bottom by a plug- 

 hole : the oil which remains after this is of an inferior quality, and can be used only 

 for factory purposes. 



The marc being crushed in a mill, boiled with water, and expressed, yields a still 

 coarser article. 



All the oil must be fined by keeping in clean tuns, in an apartment, heated to 60 

 Fahr. at least, for twenty days ; after which it is run off into strong casks, which 

 are cooled in a cellar, and then sent into the market. 



In Spain the olives are pressed by conical iron rollers elevated above the stage or 

 floor, round which they move on two little margins to prevent the kernel being 

 injured, the oil from which is said to have an unpleasant flavour. Spanish olive-oil, 

 however, is inferior to other kinds, from the circumstance of the time which elapses 

 between the gathering and the grinding of the olives. This is unavoidable on account 

 of the small number of mills, which are not in proportion to the quantity of fruit to 

 be pressed. The olives are therefore allowed to lay in heaps to wait their turn, and 

 consequently often undergo decomposition. 



The machinery employed by the Neapolitan peasants in the preparation of the 

 Gallipoli oil is of the rudest kind. The olives are allowed to drop from the trees 

 when ripe, when they are picked up chiefly by women and children, and carried to 

 the mill. The oil, when expressed, is sent in sheep- or goat-skins, carried on mules, 

 to Gallipoli, where it is allowed to clarify in cisterns cut in the rock on which the 

 town is built. From these it is conveyed in skins, to basins near the sea-shore, and 

 from these basins the casks are filled. 



According to Sieuve, 100 Ibs. of olives yield about 32 Ibs. of oil : 21 of which 

 come from the pericarp, 4 from the seed, and 7 from the woody matter of the nut. 

 That obtained from the pericarp is the finest. 



FF2 



