4 BULLETIN" 454, TJ. S. DEPARTMENT OF AGRICULTURE. 



Table II. — Yield of peppermint oil from the fresh and from the dry herb at various dates 

 of distillation and stages of growth during five successive years. 



[All yields of oil calculated on the basis of fresh herb.] 



Description 



1908 



1909 



1910 1911 



1912 



Aver- 



of material. 



Date. 



Yield. 



Date. 



Yield. 



Date. 



Yield. Date. 



Yield. 



Date. 



Yield. 



age. 



Fresh herb: 



Budding 



Flowering. . 

 Fruiting 



Dry herb: 

 Budding. . . 



July 22 



Aug. 21 

 Sept. 25 



P.ct. 



■ 0. 23 

 .20 

 .10 



July 14 

 July 24 

 Aug. 10 



July 19 

 July 26 

 Aug. 19 



P.ct. 

 0.13 



.12 



.17 



.080 

 .042 

 .052 



July 28 

 Aug. 16 

 Sept. 16 



Aug. 5 



Sept. 8 

 Sept. 27 



P.ct. 

 0.10 



.13 



.10 



.070 

 .022 

 .04S 



July 17 



Aug. 17 

 Sept. 18 



Aug. 15 

 Sept. 11 

 Oct. 2 



P.ct. 

 0.12 



.09 



.13 



.050 

 .088 

 .040 



Aug. 5 

 Sept. 21 

 Oct. 5 



P.ct. 



0.09 

 .12 

 .07 



P.ct. 



0. 134 

 .132 

 .114 



.066 













.050 













.046 















The average percentage of moisture in the budding, flowering, and 

 fruiting plants during the years 1909, 1910, and 1911 was 78.2, 74.2, 

 and 69 per cent, respectively. The yield of oils obtained from the 

 dried plants is lower in every case than from the fresh material. 

 The general average yield is approximately 50 per cent lower than 

 the yield obtained from the fresh herb at the same stage of growth. 

 It appears, therefore, that prolonged drying of the herb before dis- 

 tillation is decidedly detrimental to the yield of oil obtainable. 



In an experiment to determine what effect drying the plant has on 

 the yield and constants of the oil, Todd 1 states that no loss of oil 

 results when the plant is dried before distillation and that the color 

 and solubility of the oil from the dried plants are superior to those 

 from the fresh plants. The specific gravity, however, is slightly higher. 



From the general averages during the three successive stages of 

 growth of the plants, it appears that the yield of oil tends to decrease 

 as the plant matures. 



Information regarding the distribution of the oil in the plant was 

 obtained by custilhng separately the leaves and the tops of the plants 

 at the three successive stages of growth and comparing these results 

 with those recorded for the whole fresh herb. The results of these 

 experiments are shown in Table III. 



Table III. — Comparison of yields of peppermint oil from the fresh leaves, from the tops, 

 and from the whole fresh herb at different stages of growth during three successive years. 



Parts of plant and stage of growth. 



Yield of oil (per cent). 



1910 1911 Average 



Whole herb: 



Budding.. 



Flowering. 



Fruiting.. 

 Leaves: 



Budding.. 



Flowering. 



Fruiting.. 

 Tops: 



Budding.. 



Flowering. 



Fruiting.. 



0.13 

 .12 

 .17 



.20 

 .27 

 .13 



.20 

 .16 

 .19 



0.10 

 .13 

 .10 



.15 

 .25 



.10 

 .12 

 .OS 



0.12 

 .09 

 .13 



.26 

 .39 

 .15 



.22 

 .42 

 .19 



0.116 

 .113 

 .133 



.203 

 .303 

 .120 



.173 

 .233 

 .153 



i Todd, A. M. An experiment with peppermint plants. In Amer. Drug., v. 15, no. 9, p. 161. 1886. 



