Druckschrift 
The Edinburgh new Dispensatory : containing 1. The Elements of pharmaceutical Chemistry ; 2. The Materia Medica; or the natural, pharmaceutical and medical History, or the Substances employed in Medicine ; 3. The pharmaceutical Preparations and Compositions ; including Translations of the Edinburgh Pharmacopoeia published in 1805, of the Dublin Pharmacopoeia in 1807, and of the London Pharmacopoeia in 1815
Entstehung
Seite
CXIII
URN (Seite)
  
Rechtsdrehung 90°Linksdrehung 90°
  
  
  
  
  
 
Einzelbild herunterladen
 

Sect. 2. Pharmaceutical Operations. cxiii

and the power of absorption in fluids is much increased bycompression and diminution of temperature, although in eve-ry instance it be limited and determinate. Dr Nooth invent-ed an ingenious apparatus for combining gases with fluids ;and Messrs Schweppe, Henry, Paul, and Cuthbertson, havevery advantageously employed compression.

538. Consolidation. Fluids often become solid by enteringinto combination with solids ; and this change is always ac-companied by considerable increase of temperature, as in theslaking of lime.

DECOMPOSITION.

539. Decomposition is the separation of bodies which werechemically combined.

5i0. It can only be effected by the agency of substancespossessing a stronger affinity for one or more of the consti-tuents of the compound, than these possess for each other.

541. Decomposition has acquired various appellations, ac-cording to the phenomena which accompany it.

542. Dissolution differs from solution in being accompaniedby the decomposition, or a change in the nature of the sub-stance dissolved. Thus, we correctly say, a solution of limein muriatic acid, and a dissolution of chalk in muriatic acid.

543. Sometimes a gas is separated during the action ofbodies on each other. When this escapes with considerableviolence and agitation of the fluid, it is termed effervescence.The gas is very frequently allowed to escape into the atmo-sphere, but at other times is either collected hi a pneumaticapparatus, or made to enter into some new combination.—The vessels in which an effervescing mixture is made, shouldbe high and sufficiently large, to preveut any loss of the ma-terials from their running over ; and in some cases the mix-ture must be made slowly and gradually.

544. Precipitation is the reverse of solution. It compre-hends all those processes in which a solid is obtained by thedecomposition of a solution. The substance separated is term-ed a Precipitate, if it sink to the bottom of the fluid; or aCream, if it swim above it. Precipitation, like solution, isperformed either via huwida, or via sicca.

545. The objects of precipitation are,

1._ The separation of substances from solutions in whichthey are contained;h

I

 
Seiten anSeiten aus
Text aus