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meee ~ NoTEs. ON SCIENTIFIC RESEARCH. | 105 
rm rotatory. @) The rotation dispersion curve has either a maximum, a minimum, nor 
i! approaches a limiting value, but 4, and 4% differ greatly from the normal values. 
js 
(4) Apparent normal course of the curve fay against ve gives a straight line, but 7,, and do 
‘differ greatly from the usual normal value for the type of compound. (Relative anomaly.) 
The methods of preparation and constants of the following compounds are given 
A in the experimental part of the paper: — menthyl ester of diethylacetic acid, menthyl 
~~ ester of isopropylacetoacetic acid, ethyl ester of diphenylmethylacetoacetic acid, menthyl 
__ ester of diphenylmethylacetoacetic acid, menthyl ester of benzylacetoacetic acid, menthy] 
ester of acetylacetoacetic acid, menthyl ester of benzoylacetic acid, menthyl ester of 
Bas dibenzoylacetic : acid, monomenthy! ester of acetosuccinic acid (@- and #-forms). By 
the action of menthol. on the diethyl ester of AP ChOste eile acid, a mixture of the 
above a- and §-forms is obtained. 
With tard to the optical refraction of the resins, only isolated determinations 
had been made up to recent times. These were of very little use for practical pur- 
poses, since the methods used in the determinations were not given. That the refractive 
indices alone, and still more in connection with other physical properties, can be a 
_ valuable aid in the determination of resins of unknown origin has been shown by 
I. Greger*). Since neither the comparison methods by means of the polarisation 
microscope, nor the prism methods with the Fuess goniometer satisfied his needs, 
Greger determined the refractive indices by means of a Zeiss crystal refractometer. 
: _As comparison liquid he used Thoulet’s solution (potassium-and-mercury-iodide solution) 
__ Of refractive index 1.71813, and as source of light the sodium flame. Special methods 
- were adopted to suppress as far as possible the volatilisation of impurities which 
affected the determinations. The refractive index of the resins can be derived ale 
proximately from their melting points. 
DB: _ Greger obtained the following results:— An ie less than 1.530 is given only 
‘ by Mexican elemi, and Brazilian copal from Hymenea Courbaril; between n 1.530 and 
1.550 lie copals, elemi, benzoin, pine resins, gum lac, Umiri resin, olibanum, sandarak, 
_ dammar; between n1.550 and 1.60 lie pine resins, Chios mastix, Manila and Protium 
— elemi, as well as certain copals; above 1.60 lie gamboge, Guajac resin, Xanthorrhea 
| resin, and dragon’s blood. The refractive index is directly related to the melting 
point, hardness, density, and solubility when these are determined under equivalent 
conditions. On account of these physical constants the chemical investigation of the 
resins can be kept within narrow limits. ) ere | 
) 
Botanical Notes. 
A work by O. von Kirchner?) gives a list of ‘the diseases of our medicinal and 
spice-plants caused by fungi. The diseases named ‘leaf spot diseases’ occur very 
frequently, and are caused by the fungi of the pyrenomycetes genus Spherella_ and 
‘their closely related fruit-forms of the genus Septoria, Ascochyta, and others. Dull- 
brown or brighter spots with dark border are noticed on the leaves. They may spread 
to the stalks, and are here replaced by fungi of the genus Phoma. The rust-diseases, 
3 which appear on the stalks and leaves, may be recognised by pustules or little cushion- 
Fade Sitzungsb. d. Akad. d. Wiss. in Wien. Math.naturw. Kl., Abt. I, 128 (1919). According to kindly forwarded 
reprint. — 7%) Heil- und Gewiirzpfl. 3 (1920), 153. 
