I N D U S T R I A L A N D ENGINEERING CHEMISTRY
February, 1924
line, showing no further change in the drop weight. The curve for 3 per cent solution likewise shows a decided change in direction of the curve a t 38" C. above which the drop weight value is practically constant.
163
It is to be noted that the original gelatin with its impurities lowers the surface tension more than the ash-free gelatin, and that the 1 per cent ash-free gelatin lowers the drop weight more than the 0.5 per cent solution, which agrees with the information shown in the curves giving the relation between concentration and drop weight. VARIATION OF DROP WEIGHTWITH pH-Figs. 5 and 6 show the variation of drop weight with pH a t concentrations of 0.5 and 1 per cent. 64
d f6l t
5 58
a
55
0
ESZLI
I
2
4
0
I
1
1
I
1
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1
I
6 8 IO 12 14 16 18 AGE OF S O L U T I O NH-O U R S
FIG.7-VARIATION
20
I
I
I
22 24 26
OF DROPWEIGHT WITH AGE OF NO. 1 GELATIN
(BONE). pH = 4.2.
25°C.
VARIATION OF DROPWEIGHTWITH AGE OF SOLUTIONDrop weight measurements were made on 1 and 2 per cent solutions of bone gelatin a t a pH of 4.2 at 25" C. over a period of 24 hours, as shown in Fig. 7. Both solutions showed a slight decrease in the drop weight with age, and the curves themselves are approximately parallel. FIG..!#-VARIATION
OF DROPWEIGHT WITH pH O F 0.5 P E R CENT
SOLUTIONS AT 25' C.
Further evidence is here found for the existence of the transition point heretofore claimed as 38" C.4 In the 3 per cent solution there is a decided maximum around 30" C. Some evidence of this maximum also shows a t this point in the 1 per cent solution. PREPARATION O F ISOELECTRIC GELATIN-ISOeleCtTiC gelatin was prepared by the method described by Loeb.16 VARIATIONOF ISOELECTRIC GELATINWITH pH-Fig. 4 shows the relationship of isoelectric gelatin with pH a t 25" C. The isoelectric gelatin was made from hide gelatin No. 3. The curves show the relationship of the original gelatin with that of the isoelectric gelatin. The isoelectric gelatin can, of course, only be called isoelectric a t p H 4.7. When it is adjusted to p H values other than 4.7 it must be called ash-free. 16
J . Am. Chem. SOC.,44, 213 (1922).
Apparatus for Drying Gases' By V. T. Jackson 5701 BLACKSTONE AVE.,
CHICAGO, ILL.
H E piece of apparatus shown in the sketch has been found useful in drying gases. The small openings should be made from glass tubing having an internal diameter of 7 mm. The other dimensions are indicated in the sketch. A layer of glass wool p-3cm.4 + about 1 em. thick is placed in the bottom of --f the barrel so as to cover the two openings. Small glass beads are placed on top of the glass wool to a depth of about 10 em. Concentrated sulF' furic acid is poured over the beads until it rises about 1 cm. above them. The opening a t A is then closed with a rubber stopper. Connections are made so the gas can be aspi-
el
'=q
p-lt..-g
I
I
$
i
-1.
F I G 6-VARIATlON
OF ,DROPWElGHT AND pH OF
0.5 A N D 1
HIDEG E L A ~ INO. N 3.
PER CENT SOLUTIONS.25" A N D 40° C.
