QUANTITATIVE ESTIMATION OF CAROTINOIDS 249 



Arnaud reports indicate that he set his standard carotin solution at 

 19 mm. depth and compared his unknown solutions with this arbi- 

 trary standard. 



Arnaud (1889) used this method for the quantitative analysis of 

 the carotin content of the air-dried leaves of a large number of plants. 

 These data are shown in Table 17. Arnaud expresses his confidence 

 in their accuracy within 1 to 2 mg. of carotin for 100 grams of dried 

 leaves. The principal criticisms which can be made of this method 

 are, (1) the necessity of having a supply of pure carotin on hand for 

 making up the standard solution, (2) the failure to show that the 

 method insures the complete extraction of the carotin, (3) the pos- 

 sibility that some xanthophyll may be extracted along with the caro- 

 tin, and (4) the necessity of evaporating the petroleum ether extracts 

 to dryness before dissolving in the standard solvent, this operation 

 greatly enhancing the opportunities for oxidation and loss of pig- 

 ment. 



TABLE 17. CAROTIN CONTENT OF AIR-DRIED LEAVES (ARNAUD'S METHOD) 



Name of plant Date of Carotin 



sample content 



mg. inlOO gms. 



Rape (Brassica oleifera) June 1 189.7 



Violet ( Viola odorata) May 23 124.0 



Linden (Tilia platyphylla) May 11 79.1 



Maple (Acer pseudo-platanus) June 15 190.0 



Sycamore (Acer platanoides) June 15 178.0 



Grape (Vitis vinifera) July 12 200.0 



Wild grape (Cissus quinquejolia) May 25 145.4 



Chestnut' (Acsculus hypocastanum) May 6 118.8 



Bean (Phaseolus vulgaris) June 18 178.8 



Pea (Pisurn satirum) May 27 177.0 



Acacia (Robinia pseudo-acacia) June 8 209.0 



Peach (Persica vulgaris) June 15 114.0 



Red currant (Ribes rubrum) May 21 105.5 



Ivy (Hedera Helix) M:iy 15 50.9 



Periwinkle (Vinca Major) May 25 130.0 



Olive (Olea Europaea) July 16 75.0 



Potato (Solanum tuberosum) July 21 190.0 



Tobacco (Nicotinia tabacum) Aug. 4 178.8 



Stramonium (Datura stramonium) July 20 177.0 



Spinach (Spinacia inermis) June 1 160.0 



Beet (Beta vulgaris) July 12 183.0 



Hemp (Cannabis sativa) .June 18 215.9 



Box tree (Buxus sempervirens) June 1 86.9 



Stinging nettle (Urtica dioica) M;iy 2 171.7 



Walnut (Juglans regia) May 19 118.8 



Yew tree ( Taxus baccata) June 4 167.6 



Wheat (Triticum vulgare) June 1 167.6 



Grass (Lolium pcrenne) April 18 106.3 



Fern (Pteris aquilina) June 1 116.8 



