VOL.
NO. 8
3,
PRACTICAL CHEMISTRYFOR BEGINNERS I
Substance weighed Crucible and precipitate Crucible empty Weight of precipitate % o f ......
- - - - - - -g. -- - - - - - g. - - - - - - -g. - - - - - - - g. - - - - - - -%
887 I1
- - - - - - -8. - - - - - - -g. - - - - - - -g. - - - - - - -g.
- - - - - - -%
Simple Calorimetric Experiments* I. Determination of specific heat of a liquid from the rise of temperature when heated with constant flame. The results of this simple determination are shown in Fig. 3. 11. Mixing definite amounts of water of different temperatures and determining the final temperature. The first portion of water is stirred in a large beaker. After its temperature has become constant the second portion of higher temperature is poured into the first. The highest temperature attained is taken as final. 1Vl
11
1%
k
500 000 700 800
11.2 20.1 26.8 31.0
100 100 100 100
69.1 73.0 69.0 58.2
I I
.
20.86 27.60 32.10 33.00
l aobs.
Diff.
20.6 27.3 31.6 33.8
0.25 0.3 0.5 0.8
in % 1.25 1.10 1.50 2.90
111. When we use different liquids this method gives their specific heats. IV. The same calorimeter is used to determine the specific heats of solids. V. Determination of the melting point of tin and other substances. Compare Figs. 4, 5 , 6, and 7. VI. Cooling curve for a solution of saltpeter (Fig. 8). As I have already said this list can be extended a t will. I hope to have shown in these few examples that much experimental work is possible with moderate means.
* Hcllingmann Gondriaan, Praktische Oefeningen in Natnurkunde; Purmerund, Holland.
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Lifeless Chemicals Imitate Life Acts. ma kin^ l i f e k ~chemicals act as though they were alive is the feat reported {ram Paris by M. Herrcra, a well-known French chemist. M. Hcrrera made a solution of fourteen parts of caustic soda and one part rhoda-
havior of amoebre, one of the simplest of animal forms. They divided, moved about slowly, elongated, formed vacuoles within themselves and constantly changed their shape. Under proper conditions they kept up this performance for as long as a n hour. M. Heirera made no claim that the drops had any properties of life. The phenomenon, he said, is probahly due t o diffusion currents, changes in osmotic pressure, surface tension, and other physical and chemical influences.-Science Service
