84 REPORT OF THE COMMISSIONER OF AGRICULTURE. 



bronzed surface, the metallic powder is oxidized by the turpentine. If 

 copper-bronze powder is combined with turpentine, the bronze is first 

 oxidized and ultimately dissolved by it. Since, then, turpentine has an 

 acid reaction on copper bronzed, it will necessarily have a reaction on 

 the alkaline metals. When common oil of turpentine is added to the 

 sulphide of potassium, the potassium is oxidized, and sulphur precipi- 

 tated. In this way we may be able to explain in part the deodorizing 

 action of essential oils on soluble sulphides and gaseous sulphur com- 

 pounds. To test this, I poured an ounce of turpentine into a transparent 

 glass quart jar, in the atmosphere of which I suspended a sheet of bib- 

 ulous paper which was saturated with a composition of the iodide of 

 potassium and starch. The mouth of the jar was quickly covered with 

 a sheet of glass to exclude the action of the air. Within ten minutes 

 the paper appeared brown. The turpentine had oxidized the potassium 

 and liberated the iodine, which in turn colored the starch purple ; but, 

 to render this fact more apparent, I combined a drop of turpentine with 

 a drop of the composition of iodide of potassium and starch. When the 

 composition became visibly brown to the naked eye, and was placed 

 under a suitable power of the microscope, it was observed that many of 

 the starch granules were stained purple by the iodine. Subsequent ex- 

 periments with concentrated eucalyptus oil and the starch composition 

 gave similar results. Had these experiments been made in a pine forest 

 or plantation of JEucalypti, the liberation of the iodine, and consequent 

 coloration of the starch-paper, would have been attributed to the pres- 

 ence of ozone in the atmosphere. Nearly all the essential oils give 

 similar results when combined directly with the iodide of potassium and 

 starch. Since the preceding experiments were made, I have placed a 

 paper moistened in the starch composition in an inclosed atmosphere of 

 turpentine, placing the jar containing it in a dark closet; but the action 

 of the turpentine vapor seemed to bo as powerful in darkness as in the 

 presence of light. 



Some suppose that ozone, or active oxygen, is in great abundance in 

 the atmosphere of eucalyptus plantations, and, as a consequence, the 

 poisonous gases of marshy districts in their vicinity are decomposed by 

 it, ozone acting the part of an acid ; while others have supposed that 

 such unhealthy regions arc purified by the rapid absorption of the marsh- 

 waters, owing to the very great rapidity of the growth of the Eucahjptus 

 family. It is not my purpose to discredit the views of those who 

 attribute so much importance to the production of ozone under such 

 conditions, but to remind those who insist that oxidation of the gases of 

 malarial districts, and the consequent improved healthy condition of 

 them, in the presence of the essential oils of the eucalyptus family, or of 

 other odoriferous plants, are not necessarily the result of ozone. Any 

 acid or substance having an acid reaction will oxidize the potassium of 

 iodide of potassium. My experiments demonstrate that euoalyptol, tur- 

 pentine, benzole, or any of the essential oils will oxidize potassium when 

 it is combined with iodine or sulphur; and we are, therefore, in a posi- 

 tion to explain how the favorable changes and purifications of the 

 atmosphere to some extent are affected, independent of the theory of 

 ozone. Turpentine of commerce contains formic and succinic acid, 

 (Lowig;) but turpentine itself is an oxidizable body, as has been shown, 

 and will oxidize some foreign bodies in the atmosphere. Mix turpentine 

 of commerce with caustic potash and suspend in its atmosphere a slip 

 of paper moistened with the starch mixture ; after the lapse of twelve 

 hours it will be found that the starch is colorless or tinged yellow, instead 

 of a very dark purple ; in this case demonstrating that the presence of 



