Page:Popular Science Monthly Volume 43.djvu/99

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mists. The Arabs, therefore, were still, in the beginning of the fourteenth century, using the complicated apparatus of the Greco-Egyptians.

Alembics with several beaks were still employed by the Western alchemists in the sixteenth century. In Porta's treatise, entitled Natural Magic, a collection of processes or secret operations, the author mentions the cap of three and four beaks, each furnished with its tube and receiver. It is still the old apparatus of Zosimus. Porta, however, describes two important improvements which have come down to modern industry—graduated condensations during the same operation and the cooling worm. We need not suppose that he invented them, but only that he described the practice of his time. The new feature is as follows: In the alembics described by Zosimus the three pipes are at the same level, and doubtless disengaged an identical vapor; the ideas of the chemists of the time were too vague to allow anything else to be expected. The three tubes of Porta, on the other hand, are at different heights, and the author adds that the highest tube furnishes the purest spirit. We can already discern the ideas that have fructified in our apparatus for fractional rectification, with series of superposed chambers and trays delivering alcohols of higher degrees of concentration from the higher levels. This arrangement, however, was abandoned; at least we find no more trace of it during the following centuries. In this as in many other incidents, the men of the sixteenth century foresaw the most modern advances, but by a kind of intuition, without their having those clear notions and those exact principles of physics which, being wanting, progress is accidental and transient.

Another more durable improvement was that of the worm. The alembics of the ancient Greeks doubtless permitted distilled liquors to be obtained, but on condition of operating slowly and with a very moderate heat. In fact, the vapors were imperfectly condensed on the small surfaces of the tubes and the caps represented in the manuscripts. However little we might try to hasten the distillation, the receivers would become warm and condensation would become almost impossible. Hence the ancient authors prescribed that their apparatus should be heated over very slow fires. They operated by means of sand baths, baths of ashes, or water baths. Sometimes they tried to distill with no other heat than that of fermenting manure or a low fire of dung or sawdust. Their operations were therefore very slow, and often lasted for days and weeks. It required fourteen days, or twenty-one days, a text would say, to perform the operation. Not only did they in this way assure the effect of digestions and cementations, designed to produce gradual permeation with sulphurous and arsenical vapors, into sheets of metal submitted to the tinctorial action of