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112

S A L T S.

quality the fame ; the difference, in this refpecT,affecung only the refiduum. If lefs Nitre, it can-not afford Alkali enough to faturate the vitriolic a-cid, and the refiduum will not be a neutral, but avery acid, Salt. In this laft cafe there is one con-veniency ; the acid Salt beingreadily folubie in wa-ter, fo as to be got out without breaking the retort,which the others are not. L.

The caution, given in the laft Difpenfatory, tomake the mixture under a chimney, is very ne-ceflary to be obferved ; for, red corrofive fumeswill rife very copioufly, which are extremely per-nicious, and ought to be carefully avoided by the o-perator.

For greater fecurity, fome employ a large re-ceiver with two tubes, to the uppermoft of whichis fitted another tube, three feet long, whilft theIowermoft is inferted into a fmaller receiver, orbottle. The Swedifh Difpenfatory direclrs only areceiver, large and -properly tubulated. The Nitre,dried and powdered, being put into a retort, ofwhich it muft not take up more than one-third,and the retort being placed in a fand-heat, the vi-triolic acid is to be poured into it through a glafsfunnel, whofe ftem is long, and bent fo as to forma right-angle with its cup ; when, the apparatus

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