78 Detection of Adulterations. 



taring the oil in contact with water ; by which means if alcohol be 

 present, the volume of the water will be increased, while that of the 

 oil is diminished. If the experiment be performed in a graduated 

 vessel, the quantity of alcohol may be ascertained ; allowance being 

 made for the very small quantity of oil dissolved by the water, and 

 that adhering to the sides of the vessel. 



To discover the presence of very small portions of alcohol, M. 

 Beral proposes the immersion of a small piece of potassium to the 

 oil. If alcohol be present, the metal assumes a globular form, be- 

 comes brilliant like mercury, is oxidized, and disappears in a minute 

 or two, with a slight sound. These phenomena occur with less ac- 

 tivity in proportion as the quantity of alcohol is less. This test has 

 been found effectual in all the volatile oils tried by M. Beral, except 

 that of turpentine.* 



The adulteration of one volatile oil with another, makes the diffi- 

 culty of detection very great ; and we are here advised to compare 

 the suspected fluid with a specimen of known purity. The conclu- 

 ding remark of our authors on this subject, we prefer stating in their 

 own words, as the fact stated is new to us. " Neanmoins on a re- 

 marque qu' en imbibant de ces sortes d'huiles melangees un ligne ou 

 un papier, I'huile la plus fixe commence par se dissiper, et que celle 

 dont I'odeur est la plus penetrante ne s'evapore qu' en dernier heu, 

 etpeut ainsi etre distinguee." 



Peroxide of Manganese. — As the purity of the mineral oxide 

 varies, not only in regard to the quantity of oxygen, but from the 

 presence of foreign substances, it is very important for the artist to 

 possess the means of determining the quality of any specimen which 

 may be offered him. The process which we shall detail, is that of 

 •Gay-Lussac ; its object being to ascertain the quantity of chlorine 

 which the oxide is capable of affording. Take of the oxide to be 

 examined 61.451 -j- grains ; put it into a small matrass about two and 

 a half inches in diameter, and add about 3.861 cubic inches of strong 

 Hydrochloric acid free from sulphurous acid. Immediately insert a 

 close stopper from which proceeds a bent tube of about one tenth of 

 an inch internal diameter, its longest branch being about twenty three 

 inches in length. This branch is introduced into a long tube nearly 



* CarvijPouliot, Menthe,Camomille, Valenane,Lauiier-ceiisej Hyssope, Citron, 

 Bcrgamote, Sauge, Genievre, Roses, Romarin. 



