. Manual of physico-chemical measurements. secured by a piece of verythick platinum wire sealedthrough the bottom of theflask. On the middle neckthere is fastened a refluxcondenser with a calciumchloride tube ; the thermo-meter passes through theshorter side neck, and thelonger one, which is closedwith a cork, serves for theintroduction of the sub-stance. The boiling flask withthe glass beads, but with-out the thermometer, isfirst weighed to OOl g.,the solvent being then in-troduced and the weightagain determined. Thethermometer and con-denser are next put inposition, care being takenthat the
. Manual of physico-chemical measurements. secured by a piece of verythick platinum wire sealedthrough the bottom of theflask. On the middle neckthere is fastened a refluxcondenser with a calciumchloride tube ; the thermo-meter passes through theshorter side neck, and thelonger one, which is closedwith a cork, serves for theintroduction of the sub-stance. The boiling flask withthe glass beads, but with-out the thermometer, isfirst weighed to OOl g.,the solvent being then in-troduced and the weightagain determined. Thethermometer and con-denser are next put inposition, care being takenthat the condensed liquiddoes not flow back inthe immediate neighbour-hood of the thermometer;the asbestos jacket if isslipped over the flask, thewhole fastened on a standover an asbestos plate, andthe small flame so adjustedthat on the average one drop in ten seconds falls from the con-denser. After ■ the boiling has gone on for forty minutes thetemperature has usually become constant. The thermometer should 1 Zeit. physik. Chem., 4, 543, 186 PHYSICO-CHEMICAL MEASUREMENTS be tapped gently before reading to overcome the friction of themercury. The substance is now added, the temperature sinking afew tenths of a degree, slowly to rise again; after five minutes it hasusually reached constancy, and is then read off. If more of the sub-stance is at hand a second and a third portion are introduced. Solid substances are introduced in the form of small flat cylindersmade by means of a steel press; the rate of dissolution is muchaccelerated by the high temperature and the stirring caused by theebullition. Liquids are introduced from the pipette (Fig. 134), or ifthey are very viscous, with the valve tube (Fig. 135). On completion of the experiment the glass beads are freed from
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Keywords: ., bookcentury1800, bookdecade1890, bookpublisherlondo, bookyear1894
