. American journal of pharmacy. h thefirst portions of filtrate. If a filtering agent is used with the paperthe rate of filtration is retarded still more and may be entirelystopped while the volume of liquid absorbed, and consequently lost,is very much increased. Filter bags of felt are occasionally employed. They are usefulfor hot filtration or for syrups but are slow and permit visible parti-cles, notably starch, to pass through, so that filtrates from them arefrequently cloudy. Straining through cotton or woolen cloths isresorted to when coarse precipitates are to be separated but thismetho
. American journal of pharmacy. h thefirst portions of filtrate. If a filtering agent is used with the paperthe rate of filtration is retarded still more and may be entirelystopped while the volume of liquid absorbed, and consequently lost,is very much increased. Filter bags of felt are occasionally employed. They are usefulfor hot filtration or for syrups but are slow and permit visible parti-cles, notably starch, to pass through, so that filtrates from them arefrequently cloudy. Straining through cotton or woolen cloths isresorted to when coarse precipitates are to be separated but thismethod has only a limited application in pharmacy. There are in use devices for securing added pressure in filtrationby contriving a column of liquid several feet in height in such a way 72 Pharmaceutical Use of Filter Press. (Am jour. Pharm. /^ ^ *? February, 1917. that it may exert force upon the Hquid which is filtering. Such ar-rangements are intricate, involve an undue amount of room, andmay present difficulties in The Sperry laboratory or 10 filter press equipped with plates and frameswhich are convertible into the various arrangements used in commercial ap-paratus. It can be used as a press equipped for Thorough Washing or Simple Washing. Arrangements are provided so that either of the abovetwo arrangements can be used with separate discharge for washing or not, asdesired. Filtrate can be made to discharge from separate cocks, from eachplate or from one large cock at the head of the press. In practice the formerarrangement is called Open Discharge, while the latter is known as ClosedDischarge. It is a commercial machine in every respect. Other sizes are18, 24, 30, 36, and 42. Plates and frames can be made of iron, as shownin the cut, or of lead or wood. Added pressure secured by means of the suction pump or aspi-rator is very infrequently of use in pharmacy. The most seriousobjection to this method arises from the fact that the filtrate is neces-sarily exposed to
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Keywords: ., bookcentury1800, bookidamerica, booksubjectpharmacy, bookyear1829
