the name of a curve in the form of the figure of 8.

LEMON juice, is an article of such harmless luxury, and in some cases of such real utility, that many of our readers will be pleased to know a simple method by which they may obtain it in great purity. In the article Chemistry (Suppl.), no. 476, we have shown from Scheele and Dizé, how to obtain the citric acid perfectly pure, and in the form of crystals; but here we mean nothing more than to show how it may be completely separated from that flimsy substance with which it is always mixed in the lemon, without allowing it time to spoil or to acquire any disagreeable taste during the separation. This we are enabled to do by M. Brugnatelli, who, in the 2d volume of the Annali di Chimica, informs us, that he expressed in the common manner the juice of perfectly ripe lemons, and strained it through a piece of linen. In half an hour he strained it again, to free it from a little flimsy matter which had settled at the bottom of the vessel. He then added to the juice a certain quantity of the strongest spirit of wine, and preserved the mixture for some days in a well-corked bottle. During that time there was a considerable deposit, which to all appearance was of a flimsy nature, and which he separated by filtering paper. If the fluid was too thick to pass through the filter, he diluted it again with spirit of wine. After this operation, the deposit remained on the paper, which was entirely covered with it; and he obtained, in the vessel placed below, the purest acid of lemons combined with spirit of wine.

If it be required to obtain the acid perfectly pure, nothing is necessary but to separate from it the spirit of wine, which can be best effected by evaporation. The acid of the lemons affluens, after it has been freed from the spirit of wine and the moisture combined with it, a yellowish colour, and becomes so strong, that by its taste it might be considered as a mineral acid.

It is not necessary to evaporate the spirit of wine in a close vessel, if the experiment is made only on a small scale; nor is there any danger that in open vessels any of the acid will be lost, as it is too fixed to be volatilised by the same degree of heat at which spirit of wine evaporates. This acid has peculiar properties, which deserve farther examination.