T H E J O C’ R AT8L 0 F I S D L7ST RI .LI A
June, 1914
Ne E S G I &VE E RI
T A\
G C H E X I S T R I.’
517
NOTES AND CORRESPONDENCE FORMULA FOR CONTENTS OF CYLINDRICAL TANKS W I T H SPHERICAL ENDS
Editor of the Journal of Industrial and Engineering Chemistry: I n most all chemical plants of any size many cylindrical tanks with spherical ends are used for liquids. T o ascertain contents of these tanks by measuring the depth of the liquid inside, it is necessary to consult a curve representing the gallons per inch of depth. It is a comparatively simple matter to calculate the volume per inch of the main portion of the tank, but calculating t h a t of the spherical ends is a more complicated problem.
2
NOTE ON INFLUENCE OF RATE OF STIRRING ON TITRE DETERMINATIONS IN FATS Editor of the Journal of Industrial and Engineering Chemistry: At the time that the official method now in use in determining the Titre of Fats was adopted, i t was noted t h a t the stirring method, i. e . , continuous stirring of the fatty acids until the temperature was stationary for 3 0 seconds, gave tests higher than if the fatty acid was cooled t o the stopping point without stirring; this higher test ranged from over I ’ C. in case of oils such as Cottonseed t o only 0 .I ’ or less in the case of Stearine. Since this stirring method was adopted, the custom in this laboratory has been t o stir the fatty acids by means of a stirrer run by a water-motor and i t was soon noticed that the number of revolutions per minute of the fatty acids (the acids being revolved and the thermometer kept stationary) had a decided influence on the test. I give below a number of figures made in two different fats, the first being a Garbage Grease (Naphtha extracted) and the second a tallow: Garbage Grease
Tallow
0
TANK END The DuPont Fabrikoid Co., manufacturers of artificial leathers, use about ten of these cylindrical tanks with spherical ends. They are mostly of different sizes and I was given the task of plotting the necessary curves. I have worked out the following formula : 8-h’ ’~ ,
v m 2 -z?
‘
~~~~~
% m z - x? --z?
dz dx d y ’\-h
\a
\b
The limits are obtained from the equation of the sphere, c2 b2. x2 y2 z? = m2,where m = -
+
+ +
2b
By integration and expansion, where, A =
x
V
a3 mz-am------ac
B
c = - -a - - -
3 a6 4om3
6m
2
a r r = - ___ 6m 6
a3
-~
-
36m3 a3
1
=
3 as
80m5 9
f15
+
-h1
--h
’
5
6c
+-
a
40m3 80mj 32om’ 40c3 Substituting the value of m 2 for z in the formula, we obtain t h e volume in both ends of half the tank, VI,, By substituting h, the depth as measured for z in the formula and subtracting this volume, Vz, from VI/,, we get the volume in the ends for the desired depth of liquid, V = - Vz, or the formula becomes.
V
=
[AT
+ B T + C S ] - [Ah + Bh3 + C h j ]
L. E. CARPENTER 110 GRANDSTREET, hTEWBL‘RGH, hTEwYORK February 17, 1914
Revolutions per min 60 80 1 80 220
Stopping point 36.35 36.50
60 60 180 220
43.60 4 2 , 70 44.60 44.60
3i.20
37.40
Final highcst point 37.05 37.20 37.55 3 7 65
45.00
It will be noticed that when the speed is only 60 revolutions the first stopping point is much lower than when it is 180 or 2 2 0 , in fact, the less the speed the lower the first stopping point and as the speed is increased, the stopping point rises with each increase. I n the case of the tallow, the rate above 180 makes no difference with either temperature but with the grease a difference of 0.1’ is noted. A quite remarkable difference in the first stopping point is noted in the tallow a t 60 revolutions, although the final temperature is practically the same In my opinion, a large number of the differences between chemists on this test is due to this point. At the present time the directions state only that the acids “shall be stirred slowly,” which might mean anything. I believe that a definite rate of stirring should be specified and my judgment is that 180 revolutions should be taken as the standard, as a higher rate is rather impracticable and a lower certainly does not give correct figures. As the titre point is the highest temperature recorded by the heat of crystallization of the fatty acids, any method that will give this highest heat should be the correct one, as it is obvious that the only source of heat is from the crystallizing. In fact, a higher rate of stirring would, if anything, tend to cool the acids and so give a low test. A . G. STILLWELL i 6 1 2 PIXESr.. ~ - E WYORK M a r c h 30. 1911
A SHAKER FOR T H E MECHANICAL ANALYSIS OF SOILS Editor of the Journal of Industrial and Engiizeering Chemistry: In an article in February, 1914, THIS JOURNAL,entitled “ A Shaker for the Mechanical Analysis of Soil,” by Freeman Ward, the author makes a comparison between the shaking machine devised by him and the one used by the Bureau of Soils. He states: “The writer believes t h a t ’ h i s method is better than the one used by the Bureau of Soils in two respects. I n the first place, the machine is simple and inexpensive. A greater advantage is the saving of time. Clean separations can be effected in three hours, and in some cases two hours; this is a saving of a t least four hours over the Bureau method. If the quantity of the water used in the bottles is reduced one-half, a clean separation results in much less than three hours, but there is a tendency for the grains t o suffer some abrasion.”
