Performing A Meltingpoint Determination; Determinationof A Substancewith An Unknown; Determination Of A Substance With An Unknown Meltingpoint - Buchi 535 Handbuch

6.
6.
Performing a melting point determination
Determination d'un point de fusion
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6.1.
Determination of a substance with an
unknown meltingpoint
Preparing the specimen: Grind specimens which have
large crystals and are non-homogeneous, in a mortar, and
fill the melting point tube to a height of approx. 2 mm.
Insert the specimen tube into the specimen holder, as
described in Section 5.
Completely empty the expansion vessel (12) by twisting it
briefly upwards.
Set the main switch (1) to the ON position and reset the
temperature program by pressing the 0- button (3).
Gradually increase the nominal temperature (7) by 50° C
until the specimen melts. Read off the approximate
temperature from the display (10).
t
Set the set-point potentiometer (7) to a value about 10° C
below the temperature read off and switch on the cooling
fan 2.
As soon as the oil temperature reaches the same value
as that preselected on the potentiometer (7), switch off
the cooling fan and insert a new specimen tube.
Depending on the method used, press the button for the
required temperature rise and observe the specimen.
Observe melting of the specimen and store the tempera-
tures immediately at the beginning and end of the melting
process by pressing STO button.
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6.1.
Determination du point de fusion d'un
echantillon dont le point de fusionest
inconnu
Pn3parationde I'echantillon: Broyer au mortier les echan-
tiIIons presentant de gros cristaux ou non homogenes et
les verser dans le tube d'echantillons jusqu'a une hauteur
d'environ 2 mm.
Placer le tube dans le support d'echantillons selon para-
graphe 5.
Vider completement le vase d'expansion (12) en le tour-
nant un moment vers le haut.
Enclencher I'interrupteur principal (1) et supprimer le pro-
gramme de temperature en pressant la touche 0 (3).
Augmenter la temperature de consigne (7) par pas de
50° C.
Des que I'echantillon fond, lire la temperature approxi-
mative sur l'affichage(10).
Regler le potentiometre de consigne (7) environ 10° C en
dessous de la temperature lue sur I'affichage, enclen-
eher le ventilateur de refroidissement (2) et placer un
nouveau tube d'echantillons.
Selon la methode choisie, appuyer sur la touche corres-
pondant a la vitesse d'elevation de la temperature desiree
et observer I'echantillon.
Observer le debut et la fin de la fusion de I'echantillon et
memoriser immediatement les valeurs correspondantes
de la temperature en pressant la touche STO.
Ensuite rappeier et noter les valeurs mesurees en
pressant la touche RCL.
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