io8 PLANT PRODUCTS 



only one which does not reduce Fehling's solution (see 

 p. 107). 



The Tri-Saccharose (raffinose) is the condensed product 

 of the three mono-saccharoses glucose, fructose, and galactose, 

 and occurs in sugar beet. Its admixture with sucrose is 

 neither easy, to detect nor resolve. It does not reduce 

 Fehling's solution, and has the high rotary power [a] D =+i04. 



The Tetra-Saccharose (stachyose) is the chief carbo- 

 hydrate in the Japanese artichoke. It hydrolizes to glucose, 

 fructose, and two molecules of galactose. It does not reduce 

 Fehling's solution. 



THE FATS AND Oii,s. 



These are all compounds which have glycerine as a 

 base, and one or more of the fatty acids for the acid 

 part of the ester. Oils are obtained from seeds either by 

 pressure or by " Rendering." The latter process consists 

 in boiling the seeds with water, when the husks and fibre 

 sink and the oil rises to the surface. With modern 

 methods, extraction by solvents like petrol is employed. 

 The acids universally found are stearic (C 18 H 36 O 2 ), oleic 

 (Ci8H 34 O 2 ), and palmitic (Ci6H 32 O 2 ). Other special acids 

 in smaller amount are specific to particular plant products. 

 All the fats, on treatment with alkali, are hydrolized with the 

 production of soap and glycerine. Glycerine is miscible with 

 water, and is non-volatile, although it can be distilled in a 

 vacuum. The fatty acids, when unsaturated, absorb iodine 

 from solution, and the iodine absorption is closely connected 

 with the drying properties of the oil. Sulphur chloride acts 

 on fats rapidly. Both sulphur and chlorine are taken into 

 the molecule. These compounds are used as rubber substi- 

 tutes (see p. 165). Free sulphur also acts upon the unsatu- 

 rated oils at temperatures above 120 Cent. 



Some other materials, which are extracted by ether in 

 the ordinary analysis, do not belong to the true fats and oils. 

 These are waxes, which are often compounds of the higher 

 alcohols, and higher acids. Whilst the fats and oils have a 

 very high feeding value, the waxes have no value as food. 



