Copy 1

Practical pharmacy: the arrangements, apparatus, and manipulations, of the pharmaceutical shop and laboratory / By Francis [sic] Mohr ... and Theophilus Redwood.

  • Mohr, Francis.
Date:
1849
Catalogue details

Licence: Public Domain Mark

Credit: Practical pharmacy: the arrangements, apparatus, and manipulations, of the pharmaceutical shop and laboratory / By Francis [sic] Mohr ... and Theophilus Redwood. Source: Wellcome Collection.

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    which the lower end of it is immersed, by opening the stop-cock, during the progress of the evaporation, without affecting the vacuum. The liquid to be evaporated being introduced into the pan, and the joints all made tight, exhaustion is effected by the pump, which communicates with the receiver (K), the worm of the condenser (1), and the interior of the pan (A). When the mercury in the pressure- gauge has been reduced to a column of four or five inches, steam is conveyed through the pipe D, to the steam-chamber (C), while the water which collects here from condensation is carried off by the pipe E. The action of the pump should now be resumed, and continued throughout the process. The liquid, if aqueous, will commence boiling when heated to about 120° Fahr., and the evapo- ration may be actively kept up at a temperature varying from this pomt to 140° Fahr., according to the degree of exhaustion main- tained and the state of inspissation of the extract. The condenser must be continuously supplied with cold water, which enters through the tube M at the bottom, while the hot water passes off from the top through the tube N. It may be well to observe, that the preparation of extract of sarsaparilla by this process is attended with considerable difficulty, in consequence of the tendency of the liquor to froth up, and thus pass over into the receiver. Spontaneous evaporation, has within the last few years been very successfully applied in the preparation of extracts. This process consists in the means for effecting evaporation at the ordinary tem- perature of the atmosphere. Practically, however, artificial heat to a certain extent is generally employed, and the process is still called one of spontaneous evaporation, if conducted at the tempera- ture of a drying-room. The first specimens of extract prepared by this process were made by exposing the liquid in shallow vessels to the direct rays of the sun. Extracts of very good quality have been thus made from the expressed juices of some of our indigenous plants, such as hemlock, henbane, belladonna, dandelion, &c., by merely exposing them, in large shallow pans, in the open air, during fine warm summer weather. But the climate of this country is too uncertain to admit of the general adoption of this means of inspis- sation, and numerous contrivances have therefore been resorted to for promoting evaporation at low temperatures by artificial means. The evaporation of water and other liquids at temperatures below their boiling-points is due to the diffusion of their vapours into the superincumbent atmosphere. All gases and vapours have a tendency