To correct the ill smell of the Turpentine, they digest it with, and distil it off with Spirit of Wine. Those sophisticated with Turpentine, fired in a Silver Spoon colour it, and quickly diffuse themselves upon a Knife, or Paper. The best way to try by firing, is to put a drop or two of these Oyls on the end of a broad pointed Knife, which being first heated, and then thrust into a lighted Candle, presently take fire, and break out into a flame with much dark smoak; but if you will try them in a Spoon, heat it first over a Candle, and then blow the flame of lighted paper, or of a Wax Candle on them. To try the scent, blow out the flame of the good Oyls, and your smell will soon discover the ill scent of the Turpentine from that of the good Oyl. But on the contrary, all Oyls drawn from Plants by distillation hardly flame, and the flame soon goes out, and the smoak gives a full flavour of the Plant it self, whereas those sophisticated as before, differ from the true in both. The same Oyls are also sophisticated with cheap ones drawn from decayed Oringes, and Limons; Your smell on firing will soon discover these mixtures. A third way of sophisticating Chymical Oyls is, by mixing with them such Oyls as are made by expression, which are easily discovered by rubbing them on white paper, which being held and dryed at the fire, the Chymical part soon flyes away, and leaves the paper transparent, looking no otherwise then oyled paper; but pure Chymical Oyls totally fly away, leaving the paper white as 'twas before, and not transparent, and in this way Oyl of sweet Almonds and Spike have a great share. As for Oyls drawn by Retort, they all of them smell so strong of the fire, that neither smell nor tast can well discover any fraud in them. Now for the fixed Salts, most of them are made of the Ashes of Tobacco-stalks, &c. More might be said for the discovery of the Cheats of other Chymical preparations, which shall be reserved to another opportunity, and had Physicians just encouragement, they would spend both their time and moneys on the like discoveries for the publick Utility. Fifthly, Add to the former (though perhaps 'tis an error of ignorance only) that if such Simples are prescribed they know not, they fetch from the Herb-women what they give them, true or false; for many of these Women give to very many Plants false names; Now if the Apothecary be so careful to consult an Herbal, which few have, and fewer know how to make use of, yet they too frequently mistake the thing by reason of several names given to the same thing, or of one name to several things, and many of them consult the common Dictionaries only, which are most erroneous in the names of natural things; insomuch that in my first practice (being curious of these particulars) I have found two or three mistakes in one prescription, a Catalogue of which mistakes, and names ill given, I had collected, but the late fire consumed it, though many of them my memory hath reserved.