The mode of using the Œnokrine is as follows: ‘A slip of the paper is steeped in pure wine for about five seconds, briskly shaken, in order to remove excess of liquid, and then placed on a sheet of white paper to serve as a standard. A second slip of the test-paper is then steeped in the suspected wine in the same manner, and laid beside the former. It is asserted that 1/100,000 of magenta is sufficient to give the paper a violet shade, whilst a larger quantity produces a carmine red. With genuine red wine the colour produced is a greyish blue, which becomes lead-coloured on drying.’ I copy the above from the ‘Quarterly Journal of Science’ of April 1877. The editor adds that the inventors of this paper have discovered a method of removing the magenta from wines without injuring their quality, ‘a fact of some importance, if it be true that several hundred thousand hectolitres of wine sophisticated with magenta are in the hands of the wine-merchants’ (a hectolitre is = 22 gallons). Another simple test that was recommended at the time was to immerse a small wisp of raw silk[19] in the suspected wine, keeping it there at a boiling heat for a few minutes. Aniline colours dye the silk permanently; the natural colour of the grape is easily washed out. I find on referring to the ‘Chemical News,’ the ‘Journal of the Chemical Society,’ the ‘Comptes Rendus,’ and other scientific periodicals of the period of the phylloxera plague, such a multitude of methods for testing false colouring materials that I give up in despair my original intention of describing them in detail. It would demand far more space than the subject deserves. I will, however, just name a few of the more harmless colouring adulterants that are stated to have been used, and for which special tests have been devised by French and German chemists: Beet-root, peach-wood, elderberries, mulberries, log-wood, privet-berries, litmus, ammoniacal cochineal, Fernambucca-wood, phytolacca, burnt sugar, extract of rhatany, bilberries; ‘jerupiga’ or ‘geropiga,’ a compound of elder juice, brown sugar, grape juice, and crude Portuguese brandy’ (for choice tawny port); ‘tincture of saffron, turmeric, or safflower’ (for golden sherry); red poppies, mallow flowers, &c. Those of my readers who have done anything in practical chemistry are well acquainted with blue and red litmus, and the general fact that such vegetable colours change from blue to red when exposed to an acid, and return to blue when the acid is overcome by an alkali. The colouring matter of the grape is one of these. Mulder and Maumené have given it the name of _œnocyan_ or _wine-blue_, as its colour, when neutral, is blue; the red colour of genuine wines is due to the presence of tartaric and acetic acid acting upon the wine-blue. There are a few purple wines, their colour being due to unusual absence of acid. The original vintage which gave celebrity to port wine is an example of this.