EUFHORBIACEm. 307 



Aleuroue crystals which are found \\x many seeds. (Sachs 

 Lehrbuch der Bofanik, p. 554.) The root-bark shows numerous 



refracti\ 



emarkable 



Chemical composition. — The most important constituent of 

 the seeds is the fixed oil called castor oil, of which the peeled 

 kernels afford at most half of their weight. 



The authors of the Pharmacographia say : 



*' The castor oil of commerce has a sp. gr. of about 0-96, usually 

 a pale yellow tint, a viscid consistence, and a very slight yet 

 rather mawkish odour and taste. Exposed to cold, it dees not 

 in general entirely solidify until the temperature reaches — 18°0. 

 In thin layers it dries up to a varnish-like film. 



"Castor oil is distinguished by its power of mixing in all 

 proportions with glacial acetic acid or absolute alcohol. It is 

 even soluble in four parts of spirit of wine {'838) at 15° C.,. and 

 mixes without turbidity with an equal weight of the same 

 solvent at 25° C. The commercial varieties of the oil, 

 however, differ considerably in these as well as in some other 



respects. 



"The optical properties of the oil demand furthei' investiga- 

 tion, as we have found that some samples deviate the ray of 

 polarized light to the right and others to- the left. 



/'By saponification, castor oil yields several fatty acids, one 

 of which appears to be Palmitic Acid., Another acid (peculiar 

 to the oil) is Ricinoleic Acid, C'^H'^0''; it is solid below 

 0° C. ; does not solidify in contact with the air by absorption 

 of oxygen, and is not homologous with oleic or linoleic acid,, 

 neither of which is found in castor oil. Castor oil is never- 

 theless thickened, if 6 parts of it are warmed with 1 'part of 

 starch and 5 of nitiic acid (sp, gr. 1*25), Ricinelaidin being 

 thus formed. From this, RicinelauUc Acid may easily be 

 obtained in brilliant crystals. 



''As to the albuminoid matter of the seeds, Fleury (1865) 

 obtained 3*23 per cent, of nitrogen^ which would answer to 



