MICEOSCOPIC INVESTIGATION. 83 



inal preparations, may, therefore, be prevented from decaying by fer- 

 mentation when alcohol cannot be used successfully with them. 



The foregoing results induced me to extend my experiments to other 

 well-known essential odorous oils, first, to ascertain their relative value 

 as antiseptics and deodorizers; second, whether their oxidizing power 

 is proportional to the strength of their odors ; and, third, their imme- 

 diate chemical action on the soluble alkaline sulphides of potassium 

 and ammouiuui. For this purpose I arranged a series of test-tubes, 

 about ten inches in length by one in diameter, each of which I filled to 

 within half an inch of the top with water, adding a few drops of an 

 essential odorous oil, combining the mixture as well as could be done 

 by shaking it. All of the essential oils are sparingly soluble in water. 

 In this series of experiments I used the oils of bergamot, spearmint, 

 cloves, caraway, cinnamon, lavender, peppermint, lemon, winter-green, 

 rosemary, origanum, and cajeput. The results demonstrate that sev- 

 eral of them decompose the sulphide of potassium quickly, while others, 

 although highly odorous, are slow deodorizers, and do not seem to de- 

 compose these sulphides under the conditions stated. Eosemary, pep- 

 perment, winter-green, and lavender are of this class. 



If concentrated solutions of the oils of pennyroyal, tincture of myrrh, 

 the oil of rose geranium, and oil of horse-mint are combined in separate 

 test-tubes with sulphide of ammonium, it wiil be found that pennyroyal 

 and myrrh produce a heavier precipitate than either of the other two 

 oils, rose geranium and horse-mint. 



The oil of cloves oxidizes quickly the potassium of the sulphide and 

 precipitates sulphur when both solutions are combined in concentrated 

 form, and it also decomposes this sulphide when it is highly diluted; 

 but it exhibits no decomposing properties when combined with the sul- 

 phide of ammonium. Concentrated sulphide of potassium and ammo- 

 nium exhibit but very slight action on cajeput. Origanum decomposes 

 concentrated sulphide of potassium, while it exhibits no reaction on the 

 sulphide of ammonium. Turpentine and eucalyptol oil have a similar 

 action on the concentrated solutions of potassium and ammonium sul- 

 phides ; but the eucalyptol exhibits a higher precipitating power than 

 turpentine or any other of the essential oils with which I have experi- 

 mented. 



It is generally believed that the atmosphere of pine forests is highly 

 favorable to invalids suffering from pulmonary complaints, and it has 

 been supposed that the oxidation of the oil of turpentine exuded from 

 pine-trees, and of other essential oils, such as the odorous oils of flowers 

 in the air, is attended by the formation of ozone, inasmuch as the 

 oxidized oils and the air in their vicinity exhibit the reaction of ozone 

 with potassium iodide and starch. Kingzett attributes the active 

 properties of the oxidized turpentine-oil to the formation of monohy- 

 drated terpeue oxide C^<'ff'^OH'-0, which was shown some time ago 

 by Sobrero (Ann. Ch. Pharm., b. xxx, 106) to be formed when turpentine- 

 oil containing water is exposed to the sun's rays in a vessel filled with 

 oxygen, (see i)age 887, Watt's Chemistry, second supplement,) and it has 

 been shown that the air of the country contains an odoriferous and 

 oxidizing principle which imparts to it a peculiar odor, and the power of 

 bluing iodized red litmus paper; also of decolorizing blue litmus paper 

 without previously reddening it, and of destroying bad odors. This 

 principle is called ozone.* 



When a varnish containing commercial turpentine is applied to a 



* Ozone is supposed to be oxygen in a positive state, or allotroiiic form, having acid 

 properties. 



