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Show PRICKLY SALTWORT. 958 PRICKLY SALTWORT. tube of by Dr. Black : he first dropped a rugged pebbleinto the bed, firm a tself formedi it which of part the funnel, in some sufof ces intersti d afforde surface its on ties while the inequali upper the On liquor. ng filteri the of passage ficient size for the surface of this stone he put a thin layer of lint or clean tow; it, he dropped immediately above this, but not in contact with o the a stone similar to the former, and of a size proportionedt interThe swell in the upper part of the tube of the funnel. up filled were stices between this second stone and the funnel ly uniform on gradati with stones of a Jess dimension, and the was this , Finally ed. continuedtill pretty small sand was employ covered with a layer of coarser sand, and small stones, to sustain the weight of the fluid. A filter of sand being thus constructed fresh in the funnel, it was washed perfectly clean by making ty of extremi lower the from d droppe it fill it water pass through using if, the funnel perfectly clear and transparent ; and before might rewater no that days, some for stand to it was allowed main among theinterstices of the sand. Fromthe spongynature of the residaum which remains upon thefilter, and especially if we use that of sand, a considerable quantity of the solution of potash will be retained. It is, rs to disturb ever, easily obtained by pouring gently overit, so as it as little as begins again ence of their swims above possible, a quantity of water ; the ley immediately to drop from the funnel; and as, fromthe differspecific gravity, the water does not mix with it, but the it, the whole ley passes through before any of whole water. By means of the taste we easily learn when the Jey has passed. As it is natural to suppose that the strongest solution will pass to agitate the whole first, and the weakest last, we are directed together to rendertheir strength uniform. it If the solution of potash be pureit will be colourless, and with ate precipit a form nor acids, with will neither effervesce carbonate of potash. If it effervesces, carbonic acid is pe solution with alittle and must be separated byagain boiling the as long as it pear lime, or by dropping into it lime water any precipitate. bt If, on the contrary, it contain lime, tion, it may he much ofit having been employed in the prepara coe oi the of on separated by dropping into theley asoluti potash, * of n solutio our purified potash. When wehave thus must be again filtered. MEDICAL USE. The solution of caustic potash, under various names, has at different times been celebrated as a lithontriptic, and as often fallen again into disuse. The very contradictory accountsofits effects as a solvent are now, in some degree, explicable, since it has been discovered that urinarycalculi are verydifferent in their natures, so that some of them are only soluble in acids, and others only in alkalies. Of the last description are the calculi of uric acid, which are very frequent, and those of urate of ammonia. On these, therefore, alkalies may be supposed to make some impression ; andthat alkalies, or alkaline carbonates, taken by the mouth, have occasionally relieved calculous complaints, is certain. It is, however, said that their continued use debilitates the stomach; and M. Fourcroy has proposed applying the remedy immediately to the disease, by injecting into the bladder a tepid solution of potash or soda, so dilute that it can be held in the mouth. Before the alkaline solution be injected, the bladder is to be completely evacuated of urine, and washed out with an injection of tepid water. After the alkaline injection has remained in the bladder half an hour or more, it is to be evacuated, and allowed to settle. If, on the addition of a little mu- tiatic acid, a precipitate be formed, we shall have reason to conclude that the calculus contains uric acid, and that the alkali has acted on it. Very diluted alkaline solutions may also be taken into the stomach as antacids, but we possess others which are preferable. Externally alkaline solutions have been more frequently used, either verydilute, simply as a stimulus, in rickets, gouty swellings, and spasmodic diseases, or concentrated as a caustic, to destroy the poison of the viper and of rabid animals. Porasu, FORMERLY STRONGEST Common Caustic. (Potassa, olim Causticum Commune Acerrimum. E.) Take of the solution of potash, any quantity : Evaporate it in a covered very clean iron vessel, till, on the ebullition ceasing, the saline matter flows gently like oil, which happens before the vessel becomes red. ‘Then pour it out on a smooth iron plate; let it be divided into small pieces beforeit hardens, and immediately deposited in a well-stopt phial. s 2% |