OLEUM OLIV^. 419 



subjected to moderate pressure in a screw press. The oil thus obtained 

 is conducted into tubs or cisterns containing wat^r, from the sui-face of 

 which it is skimmed with ladles. This is called Virgin Oil. After it 

 has ceased to flow, the contents of the bags are shovelled out, mixed 

 with boiling water, and submitted to stronger pressure than before, by 

 which a second quality of oil is got. If the fruit is left for a consider- 

 able time in heaps it undergoes decomposition, yielding by pressure a 

 very inferior quality of oil called in French Huile feiTnetitee. The 

 worst oil of all, obtained from the residues, has the name of Huile 

 tournante or Huile d'enfer. 



It is said that in some districts the millstones are so mounted as to 

 crush the pulp without breaking the olive-stones, and that thus the oil 

 of the pulp is obtained unmixed with that of the kernels.^ We have 

 made many inqviiries in Italy and France as to this method of oil-making, 

 but cannot find that it is anywhere followed. 



The fixed oil of the kernels of ripe olives has been extracted and 

 examined by one of us (F.) Though the kernels have a bitterish taste, 

 the oil they yield is quite bland ; by exposure to the vapoirr of hypo- 

 nitric acid, it concretes like that of the pulp. If the whole of it were 

 extracted in making olive oil, it would only be about as 1 part of oil of 

 the keimel, to 40 parts of oil of the pidp. 



Description — Olive Oil is a pale yellow or greenish yellow, some- 

 what viscid liquid, of a faint agreeable smell and of a bland oleaginous 

 taste, leaving in the throat a slight sense of acridity.^ Its specific 

 gravity on an average is 0-916 at 17°'5 C. In cold weather, olive oil 

 loses its transparency by the separation of a crystalline fatty body. 

 The deposition takes place at a few degrees above the freezing point of 

 water, and in some oils even at 10° C. (50° F.) If the oil is allowed to 

 congeal perfectly, and is then submitted to strong pressure, about one- 

 third of its weight of solid fat may be separated. After repeated 

 crystallizations, this fat melts at 20 to 28° C. The fluid part or Olein, 

 continues fluid at - 4° to - 10° C. Olive oil belongs to the class of the 

 less alterable, non-drying oils. 



The foregoing description does not apply to the inferior sorts of oil, 

 which congeal more easily, are more or less deep-coloured, have a dis- 

 agreeable odour and taste, and quickly turn rancid. These inferior oils 

 have their special applications in the arts. 



Chemical Composition — The chief constituent of olive oil is Olein 

 or more correctly Triolein, C^H^(O.C^^H^O/, identical so far as at present 

 ascertained with the fluid part of all oiLs of the non-drying class. The 

 proportion of olein in olive oil, as well as in other oils, is liable to 

 variation, the result partly of natural circumstances and partly of the 

 processes of manufacture. The best oils are rich in olein. 



As to the solid part of olive oil, Chevreul believed it to be constituted 

 of Margann, which he first examined in 1820. But Heintz (18.52 and 

 later) showed margarin to be a mixture of palmitin with other compounds 

 of glycerin and fatty acids. Collett in 1854 isolated Palmitic Acid, 



^ TAeCrocer, April 25, 1868, supplement; and therefore in the freshest condition; 



Pereira, Elem. of Mat. Med. ii. (1850) 1505. but the acrid after-taste is more perceptible 



- This according to our experience is the in oil which has been long kept, 

 case even mth oil as it runs from the pulp 



