Scientific and other notes on essential oils. 5 



testing the oil with the object of examining its applicability for flotation purposes. The 

 oil produced from "black sage" has a certain resemblance to the eucalyptus oil found 

 in the Australian Eucalyptus amygdalina. A considerable quantity of oil from Artemisia 

 tridentata was divided into fractions which were tested for their fitness for the flotation 

 of various minerals, such as galena, pyrites §c. A tar oil fraction appeared to be 

 specially suitable for this purpose, with which quantitative experiments were made on 

 zinc, quicksilver, lead and gold-silver ores; the abstract, however, gives no particulars 

 as to the results obtained. 



According to G. D. van Arsdale 1 ), the various oils do not act in the same sense 

 when applied for flotation purposes. One group of them is suitable for forming a thin 

 coating over the particles of the sulphides; these are called "oilers", the others 

 "foamers". The latter produce the froth and thereby reduce the surface tension of the 

 water. The froth only acts by increasing the surface and is, in consequence, dis- 

 pensable. When forming an emulsion, an oil becomes ineffective. The use of sulphuric 

 acid leads to the disappearance of any emulsion which may have been formed. The 

 favourable effect of the addition of acids must be attributed to this quality. Instead 

 of mixing the oils at the outset" it is much more advantageous first to add the "oilers" 

 and then to run the "foamers" in, when the former have enveloped the particles of 

 the sulphides. 



According to H. J. Stander 2 ), the intermediate surface tension between water and 

 particles of sulphide is increased by the addition of oil and its bearing power is 

 enhanced. Whereas pine tar drives the colloids into the froth, coal tar does not have 

 this effect. Probably the particles of sulphide are charged with positive electricity in 

 the flotation process, those of quartz with negative electricity. 



Bay Oil. Besides the genuine bay tree a variety, Pimenta acris var. citrifolia is 

 to be found in the West Indian Islands, which, owing to the lemon-like smell of its 

 leaves, is termed "Lemoncilla", "Bois d'Inde citron" or "False bay" and whose leaves 

 are also called "Citronella leaves". The oil derived from them contains large quantities 

 of citral and cannot really be termed bay oil 3 ). 



It goes without saying that in starting a plantation of bay trees attention must be 

 paid to the fact that this inferior variety is not included amongst the other plants. 

 This error, however, was committed 4 ) in the trial plantation on the Isle of Tortola; 

 in fact it was proved at a recent examination that 35 per cent, of the seedlings there 

 present belonged to the lemon-like-smelling variety. It appears that the mother plant 

 was a hybrid. The leaves looked quite normal and nothing but their odour betrayed 

 the fact that they belonged to the inferior species. 



Betel Oil. On page 32 of our April Report 1914 we published an investigation 

 by Mann, Sahasrabudha and Patwardhan on the physiology and chemistry of betel 

 leaves which are in general use in India for chewing purposes. In a recent publication, 

 H. H. Mann and V. G. Patwardhan 5 ) referred again to this subject. The betel leaves 

 suitable for chewing are generally mature or over-mature and not yet brittle. In leaves 

 which are not yet mature and are still growing, the percentage of starch, non-reducing 



x ) Eng. Min. Journ. 101 (1916), 851; Zeitschr. f. angeic. Chem. 30 (1917), II. 129. — 2 ) Eng. Min. Journ. 

 101 (1916), 756; Zeitschr. f. angew. Chem. 30 (1917), II. 129. — s ) Comp. Gildemeister und Hoffmann, Die 

 atheri$chen Ole, 2 nd ed., vol. Ill, p. 204. — *) Perfum. Record 7 (1916), 303. — 6 ) Mem. Dep. Agric. India i 

 (1916), 281; Journ. Soc. chem. Industry 35 (1916), 1033. 



