§ 136. ETHEREAL OILS. 117 



AnihoxantMn, the yellow colouring matter in the petals of many 

 flowers, also differs from xanthophyll. It occurs in two varieties, 

 one of which (anthochlor, xanthein) is soluble in water, whilst the 

 other (xanthin, lutein) is dissolved only by ether and alcohol. The 

 latter turns green and blue on the addition of hydrochloric acid. 



ETHEREAL OILS, VOLATILE ACIDS, ETC. 



§ 136. Estimation. — The following estimations are taken from 

 Osse, and given here in illustration of the method recommended 

 in § 22 : 



I. 0*277 gram of oil of turpentine was diluted with petroleum 

 spirit to 10 cc. ; 1 cc. of the solution was evaporated as described 

 in § 22. The weight of the residue was 0-046 gram, which, after 

 exposure to the air for 1 minute, decreased to 0"026 gram (differ- 

 ence, 0-02) ; after a second minute's exposure, 0'0205 gram (dif- 

 ference, 0-0055); after a third, 0-017 gram (difference, 0-0035); 

 after a fourth, 0135 (difference, 0-0035). The weight of the 

 turpentine taken is calculated from the third weighing, 0-0205 

 gram, to which is added 2 x 0-0035 gram, making a total of 0-0275 

 gram from 1 cc, or 0-275 gram from 10 cc, instead of 0-277 

 gram. A second estimation gave 0-267 gram ; mean 0-271 gram. 



II. 0-1268 gram of oil of lemon was diluted to 5 cc. with petro- 

 leum spirit, and 1 cc. taken for evaporation. 



1st weifrhinrr = O'OöOS 



To the third weighing, 0-0185 gram, there is to be added 

 2 X 0-002 gram, giving a total of 0-0225 gram from 1 cc, or 

 01125 gram from 5 cc, instead of 0-1268 gram. A repetition of 

 the estimation gave 0-1275 gram; mean 0-1200 gram instead of 

 0-1268 gram. 



III. 0-166 gram of oil of cinnamon diluted to 10 cc ; 1 cc. 

 taken for evaporation. 



1st weighing = 0-0317 



2nd ,, --= 0-0171 difif. = 0-0146. 



3rd „ = 0-0163 ,, = 0-0008. 



4th ,, = 0-0160 ,, = 0-0003. 



5th ,, = 0-0157 „ = 0-0003. 



The third Aveighing, 0-0163, represents the quantity of oil 

 present, since no correction has to be made, as the co-efficient of 



