nm… ANALYSIS
'
15
until the eutectic concentration is reached.
The crystallisation of this mixture ’ is shown
at — 27 .5°C by the start of an exothermic reaction. This is completed at about —- 33°C
when the resistance shows a sudden increase to over
1 Mes.
On warming, the reverse of
these effects is seen.
As the temperature
rises to the eutectic temperature, in this case
—
21.6°C, there is an endothermic reaction as ionic mobility returns accompanied by a
sharp fall in resistance. The di‘erence in temperatures at which these phenomena occur
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FIGURE 4. Thermal analysis of a mixture of 0.9 % calcium chlôride and 0.9 % sodium Chloride in water.
Note the two eutectic points on the di'erential together With the increase in conductivity as the lower eutectic
mixture thaws.
…
on cooling and warming represents the degree of Supercoolingof
Figure 4
represents the analysis of a mixtureof O_.9 % calcium_ehlodeand 0:9 %
It Will be seen that both euteotics are clearly shown on 1=the dierential,temperaære Whilst
the resistance change coeurs at the lower eutectic
calcium
chloride.
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—
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Experiments With Horse Serum (gure5)
showed that— the 5IGSISÊIVIÎY
increases regularly during the cooling— andthey=
at —— 55° and
——
50°C respectively, When—the
is over
areat,——
and
_
25°C respectively and fo;
preservation Èofzallgpropertiesit is therefore better to dry
below these temperatures}
supercool and shoùldtherefore; be cooled
at least another ten degreeslower
ThCSSJŒSU1ÎS “are similar to those—of Rey
(1960). The use of serum as a freeze—drÿing protective suggested that the prog—_:e5srye
increase
resistance « maybe signicant
to biologiçaIS-ç « Thermal.
s1yœr01 save
,,
a:_s_imilar gradual
as Previously
no;£rçäl
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