According to a notice published in the "Deutsch-Amerikanischen Apotheker Zeitung," vanillin adulterated with benzoic acid has occurred in the United States. A sample subjected to examination is said to have been nothing but benzoic acid perfumed with vanillin. Such an adulteration can be detected with the microscope, since vanillin crystallizes in acicular crystals, and benzoic acid in lamina, which can be readily recognized. Pure vanillin melts at 176° F., while the melting points of such mixtures are considerably higher, it being in one case at 249° F. By extracting such mixture with thin sodium carbonate solution, benzoic acid passes into solution. After neutralizing with hydrochloric acid, the filtrate yields with ferric chloride a fawn-brown precipitate of ferric benzoate, and on adding hydrochloric acid in excess, the benzoic acid, which dissolves with great difficulty in cold water, is precipitated. By treating the latter, or the ferric benzoate, with dilute sulphuric acid and magnesium, the benzoic acid is reduced to benzaldehyde, which is recognized by its characteristic odor of oil of bitter almonds. _Nitrobenzol_ is obtained by treating benzol, or a mixture of it, with toluol and their higher homologues, with strong nitric acid, or a mixture of nitric and sulphuric acids, washing the product of reaction with water and soda, caustic soda or ammonia, expelling the unaltered hydrocarbons with steam and rectifying the residue. Three varieties distinguished by their boiling points and odor occur in commerce. The nitrobenzol or oil of mirbane (_essence de mirbane_) is the so-called _light nitrobenzol_, which boils at from 401° to 415° F. The _heavier_ varieties boil at a higher temperature and have a more or less disagreeable odor; they are used in the manufacture of aniline and aniline colors. Pure oil of mirbane is pale yellow, the finest qualities being colorless and almost as clear as water. It has an agreeable odor resembling that of oil of bitter almonds, a specific gravity of 1.186 to 1.2 = 25° Bé., and congeals at 37.4° F. to a crystalline mass. It is scarcely soluble in water, sparingly so in alcohol and with difficulty in watery spirit of wine; it is miscible in all proportions with ether, benzine, volatile oils, and most fat oils. Oil of mirbane is largely manufactured in England, but the German product is now generally preferred, it being purer and does not impart to soap perfumed with it a yellowish tinge. The finest oil of mirbane is prepared from pure crystallizable benzol, and again purified by washing with potassium bichromate and sulphuric acid, and by rectification with steam. Pure nitrobenzol suffers no change by boiling with soda lye, while the poorly rectified product colors the lye yellow or brown.