. A treatise on pharmacy for students and pharmacists. om of thevessel. Enamelled cast-iron dishes areextensively used, but, owing to thenon-uniform expansion and contrac-tion of the metal and enamel, the latteris apt to crack and chip off, unless heatbe very carefully applied; the so-called agate ware dishes are better,being made of sheet-iron and thenenamelled. For neutral liquids, well-tinned copper pans may be employed,while for the evaporation of solutionsof caustic soda or potassa, silver orperfectly clean iron vessels are neces-sary. Evaporation of liquids in open ves-sels is materially
. A treatise on pharmacy for students and pharmacists. om of thevessel. Enamelled cast-iron dishes areextensively used, but, owing to thenon-uniform expansion and contrac-tion of the metal and enamel, the latteris apt to crack and chip off, unless heatbe very carefully applied; the so-called agate ware dishes are better,being made of sheet-iron and thenenamelled. For neutral liquids, well-tinned copper pans may be employed,while for the evaporation of solutionsof caustic soda or potassa, silver orperfectly clean iron vessels are neces-sary. Evaporation of liquids in open ves-sels is materially facilitated by keepingthe liquid in motion, which, in smalloperations, can be readily done bystirring with a glass rod or porcelainspatula, and on a large scale by meansof a mechanical stirrer operated bysteam or water power. A simple formof mechanical stirrer is shown in ; it was devised by John Moss, ofEngland, and consists of a 1J inch shaft, A, and a hollow shaft, B,which readily slides over it. These shafts are fastened together at C, 3C. Moss mechanical stirrer. SEPARATION OF VOLATILE MATTER. 157 by means of a pin, and are held vertically over the centre of the evap-orating pan by means of the brackets, D, attached to the wall. Powerfor turning the shaft is supplied by a band passing around thegrooved pulley at E. To the lower end of B is attached a hard-woodblock, on the opposite sides of which are fastened the stirring paddles,F, which can be set at any desired angle, by means of winged-screwbolts, as seen in the cut. The paddles, which are usually made ofash, may consist of solid blades, 2 feet long by 2J inches wide and§ inch thick, but are preferably perforated with holes not less than 1inch in diameter, which prevent the contents of the pan from mov-ing around as a solid mass, and insure the formation of currentsof different sizes, moving at different rates of speed, whereby evap-oration is greatly facilitated. ? Corrosive vapors are sometimes given off dur
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Keywords: ., bookcentury1800, bookdecade189, booksubjectpharmacy, bookyear1895
