LINEN 



125 



. A sulphide of cobalt, named after the Swedish naturalist, Linn6 

 (Linnaeus). See COBALT. 



XiIKTSEED. ( Graine de lin, Fr. ; Lcinsaine, Ger.) . The seed of the flax, Linum 

 usitatissimum, which is indigenous to our islands, and is cultivated extensively in this 

 and other countries for its seed, and ion flax. Linseed contains in its dry state, 11-265 

 of oil; 0-146 of wax; 2-4808 of a soft resin ; 0'550 of a colouring resinous matter; 

 0'926 of a yellowish substance analogoiis to tannin ; 6'154 of gum ; 15"12 of vegetable 

 mucilage; 1-48 of starch ; 2-932 of gluten ; 2'782 of albuminc ; 10'884 of saccharine 

 extractive ; 44'382 of envelopes, including some vegetable mucilage. It contains also 

 free acetic acid ; some acetate, sulphate, and muriate of potash, phosphate and sulphate 

 of lime ; phosphate of magnesia ; and silica. 



XiXXXSE&D OIXi is obtained from linseed by first bruising the seeds, grinding them, 

 and subjecting them to violent pressure, either by means of wedges, or of the hydraulic 

 or screw press. Cold drawn linseed oil is obtained cold, and is paler coloured, less 

 odorous, and has less taste than that which is obtained when heat is applied. 



It is usual to employ a steam heat of about 200 Fahr. By cold expression the seeds 

 yield about 20 per cent., while by the aid of heat nearly 27 per cent, of oil can be 

 obtained. The ultimate composition of linseed oil is carbon 76'014, hydrogen 11-351, 

 and oxygen 12'635; its proximate constituents being oleic and margaric acids, and 

 glycerine. Linseed oil is much used as a vehicle for colours by the painter. If 

 linseed oil is exposed in a thin coat to the air it absorbs oxygen and becomes tenacious, 

 and in many respects like caoutchouc : upon this property mainly depends its use in 

 the arts. To secure this more readily a drying process is adopted, which must be 

 described. 



When linseed oil is carefully agitated with acetate of lead (tribasic acetate of lead), 

 and the mixture allowed to clear by settling, a copious white cloudy precipitate forms, 

 containing oxide of lead, whilst the raw oil is converted into a drying oil of a pale 

 straw colour, forming an excellent varnish, which, when applied in thin layers, dries 

 perfectly in twenty-four hours. It contains from four to five per cent, of oxide of 

 lead in solution. The following proportions appear to be the most advantageous for 

 its preparation : 



In a bottle containing 4 pints of rain water, 18 ounces of neutral acetate of lead are 

 placed, and when the solution is complete, 18 ounces of litharge in a very fine powder 

 are added ; the whole is then allowed to stand in a moderately warm place, frequently 

 agitating it to assist the solution of the litharge. This solution may be considered as 

 complete when no more small scales are apparent. The deposit of a shining white 

 colour (sexbasic acetate of lead) may be separated by filtration. This conversion of 

 the neutral acetate of lead into vinegar of lead, by means of litharge and water, is 

 effected in about a quarter of an hour, if the mixture be heated to ebullition. When 

 heat is not applied, the process will usually take three or four days. The solution of 

 vinegar of lead, or tribasic acetate of lead, thus formed, is sufficientfor the preparation 

 of 22 Ibs. of drying oil. For this purpose, the solution is diluted with an equal volume 

 of rain-water, and to it is gradually added, with constant agitation, 22 Ibs. of oil, with 

 which 18 ounces of litharge have previously been mixed. 



When the points of contact between the lead solution and the oil have been fre- 

 quently renewed by agitation of the mixture three or four times a day, and the mixture 

 allowed to settle in a warm place, the limpid straw-coloured oil rises to the surface, 

 leaving a copious whitish deposit. The watery solution rendered clear by filtration, 



