H2-115] OIL-CAKES 43 



* 112. Woody Fibre in Oil-cakes.— The woody 

 fibre and the sand are the indigestible portions of oil-cakes. 

 Woody fibre may be shown to be present in oil-cake in the 

 following way. 



Take as much ground linseed-cake as can be held on a 

 sixpence, place in a test-tube, and fill the test-tube about one- 

 third full of glycerine. Now heat very cautiously in the 

 Bunsen flame until the glycerine just boils. Keep it hot 

 for about a minute, then allow it to cool. Nearly fill 

 the test-tube with water, warm again, and filter. The sub- 

 stance left on the filter will be nearly pure woody fibre. 



* 113. Sand in Oil-cake. — Burn a little oil-cake powder 

 on platinum foil over the Bunsen flame, in the same way as 

 was described with bones in paragraph 97, until the ash is 

 quite light-coloured. Empty the ash into a clean test-tube 

 and fill it about an inch deep with dilute hydrochloric acid. 

 Boil for a minute or so, then filter. Spread out the filter on 

 a glass plate ; grains of sand, if present, will be seen on the 

 paper. ThiS experiment may not always succeed on the 

 first attempt owing to the small amount which can be 

 burnt at once on a piece of foil. Two or three attempts will 

 usually give some sand, especially if the same filter be used 

 for all the experiments. 



114. Linseed-cake. — All the above tests are applicable 

 to any kind of oil-cake, but some few tests may be per- 

 formed with special kinds of cake. A pure linseed-cake 

 may generally be recognised from two of its properties. It 

 is highly mucilaginous, and it does not contain starch. 



115. Mucilage in Linseed-cake.— Place about a 

 teaspoonful of ground linseed-cake in a 4-ounce beaker and 

 half-fill the beaker with boiling water. Stir vigorously with 

 a glass rod ; allow to cool. It will be found that the linseed 

 has swollen up into a gummy mass. The better the cake, 

 the more mucilaginous the mass will be; whilst a very 

 poor cake will not swell up at all, but settle quickly to the 

 bottom of the liquid. 



