1436
INDUSTRIAL AND ENGINEERING CHEMISTRY Table I-Results
SAMPLE
TYPEMINERALOIL
SOAP
Type
Amount
%
Ala A1 A1 AI AI
10 10 10 10 10
600 S. R.,e 200 vis. a t 210 600 S R 200 vis a t 210 600 S'R" 200 vis: at 210 600 S' R" 200 vis. a t 210 600 S: R:: 200 vis. at 210
6
A1 A1 A1 AI A1 Soda
10 10 10 10 10 10 7 18
300 vis. a t 2109. R. 300 vis. at 210 S. R. 300 vis. oxidized stock 200 vis. bright stock 200 vis. bright stock 200 vis. brjght stock 200 vis. bnght stock 200 vis. S. R.
14 Soda 15' Soda
10 15
150/160 bright stock 160/160 bright stock
7 S
AI
9
Ai
io 11 12 13
of Teats on Samples of Rocker-Arm Greases PENEMCTRATIMEIN ROCKERARM
MOISTVRE
MICHAELTION MELTING UNTIL DRYAT: V1S.b AT 77 POINT 200' F. 250' F. 300" F;
(83.3" (121.1" (148.9
%
1 2 3 4 5
Vol. 23, No. 12
...
None Trace None None None
.60. . . ... 97 ..,.. ... 145
None
84 75 235 197 198 129 48
0.2 None None None None None
... ... ... .. .... ... ... ...
75
... ... ...
... ... ... ... ... ...
' P.
C.)
(O
C.)
.... .... .... .... .... .... .... ... ... ... ...
208s 156'(68.9)
253 180 82 2) 231 258 ($24.4)
... ... ... ... ... ...
.... .... .... .... .... ....
Hours 51
..* .
.. .. .. 12
.. 22
14
..
31
..
.. a .
....
C.)
C.)
Rours Rours 40 26 17 28 .11. 27 4 . . 22 8
.. ..
..
14 1s 12
.. 27
..
.... ..
RESULTSOF FIELD BXPT.AND REMARKS
lOI/i
11 . 7 6 15 50 45 8
Satisfactory in dry climate Broke down in 15 t o 20 hours Satisfactory in dry climate Same results as in (1) and (3) Chem. composition similar to (1)but contains some dioleate Same comDosition a8 ( 8 ) , but moist Fair in drv climate Not muc6good in any climate Results irregular Results irregular Fair in dry climate Good for push rods;d better than (14) and (15) Good for push rodsd Good for Dush rods in hot en- ' ginesd'
N a a n d AI 15 200 vis. S.R. 134 21 N a a n d AI 15 200 vis. S.R. 74 1 . 12 Soft etrolatum 87 33 39 *. 9 Used a t St. Louis airport 19 Hart?petrolatum 50 50 45 .. 10 20 Hard petrolatum 67 33 156 *. 17 21 Hard petrolatum 87 33 164 16 0 All aluminum soap reages prepared a t the Texas Pacific Coal & Oil Co. were made by stimng the soap into the coal oil, heating to 290' or 300" F (143.3' or 148.8' C.), whik stirring and drawing off immediately. b McMichael viscometer a t 100' F. (37.S0C.); spindle, 1 cm. diameter, 3 cm. immersion. C Wooden cone weight 12.09 grams. d Not recornminded for rocker arm proper because of danger of damage owing to stiffness of grease. Steam-refined stock of 600' F. (316' C.)Flash (Cleveland open cup).
16 17 18
...
arm machine was run always under substantially the same conditions. It is fairly certain that the knock-rating of the gasoline employed has a great deal to do with the lasting qualities of the rocker-arm greases, as knocking gasoline causes higher cylinder temperatures, If non-detonating gasoline is used, temperatures not in excess of 350" F. (176.7' C.) around the rooker-arm boxes are to be expected. Reports of certain tests carried out a t various airports claim higher temperature, however. Unfortunately it has not been possible to ascertain the knock-rating of the fuels used in these tests. Existing Specifications
DifEculties of a nature similar to those described here were experienced by the Air Corps of the United States Army. As will be remembered, the Army in insuing specification Y-3558 for rocker-arm lubricants did not specify any consistency, and the only requirement is that the grease shall be a homogeneous mixture of minerdoiland pure odorless aluminum soap containing no filler. The United States Navy in specification E l 0 0 designates aluminum-soap greases containing at least
..
..
..
.. ..
.
15 per cent of aluminum stearate or palmitate, and having an A. S. T. M. penetration of 300 to 360. It is found here that this specification can include greases from the poorest to almost the best. On the other hand, the very best aluminumsoap grease found here so far contained only 10 per cent soap. The present situation calls for a thorough study and the development of new tests. Pressure viscosities a t temperatures of from 0" to 350" F. (-17.8" to 176.7' C.) are necessary. Tests for the adhesive and cohesive qualitiee, resistance to hydrolysis, and breakdown upon continuow pounding should be found and developed. Possibly the Knopf adherometer (3) may give some information. The service test employed in these laboratories gives a good indication, but owing to the fact that the tests can be run under a single atmospheric condition only, it9 application is not wide enough. Literature Cited (1) Faraghu, W.F., et al., U. S. Patent 1,550,608(Aug. 18, 1925). (2) Henry, R. W.,e t al., U. S. Patent 1,891,882(Nov. 13, 1828). (3) Knopf, C. L., Am. Petroleum Inst. "Methods of Testing Automobile Gear Lubricants," December, 1928.
Hydrolysis of Starch by Carbonic Acid' Milton A. Dewey' and Norman W. Krase DEPARTMENT OF CHEMISTRY,UNIVERSITY OF ILLINOIS,URBANA, ILL.
HIS l a b o r a t o r y has
The hydrolysis of starch to reducing sugars can be to a s o l u t i o n c o n t a i n i n g p r e v i o u s l y repo&d effected by carbon dioxide solutions in water at eleabout 10 per cent by weight preliminary work on vated pressures and temperatures. The rates of hyof acetic acid. m e the p r o p e r t i e s of aqueous drolysis at 156", 18609 and 216" C. and at 1000 pounds only a m o d e r a t e concentra(70.3 kg.1 carbon dioxide Pressure are linear functions tion of a c i d , t h e a u t h o r s solutions of carbon dioxide of time. It is still uncertain whether or not this rewere, n e v e r t h e l e s s , enunder pressures of carbon dic o u r a g e d to make further o x i d e U P t o a b o u t 2500 action is monomo~ecu~ar. studies of the propertiea of pounds per square inch (175.8 kg. per sq. cm.). This work ( 1 ) indicated that car- carbonic acid under pressure by other methods. Jenkinson bonic acid could displace acetic acid from aqueous solutions (3) began work on the hydrolysis of starch by carbonic of calcium acetate until the resulting acidity corresponded acid and his results indicated the feasibility of obtaining glucose sirups by this treatment. Kleiderer and En& (4), 1 Received August 28, 1931. using Jenkinson's apparatus, studied the hydrolysis of inulin * Present ad&-, Midcontinent Petroleum Corp., Tulsa, Okla.
T
IYDUSTRIAL AND ENGINEERING CHEMISTRY
December, 1931
under pressure. They found that satisfactory conversion products could be obtained with carbon dioxide, nitrogen, and sulfur dioxide, there being very little difference between the results when using nitrogen and when using carbon dioxide. The present work is confined to a study of the hydrolysis of starch at several temperatures, using carbon dioxide at about 1000 pounds (70.3 kg.) pressure. Experimental Method
The apparatus was essentially the same as described by Kleiderer and Englis (4). Charging of the reaction chamber was accomplished by forcing a starch-water suspension into the chamber by means of carbon dioxide pressure. This method made it possible to heat the chamber to the desired conversion temperature before charging and practically to eliminate, therefore, the initial period of heating the starch solution.
with a golden brown color characteristic of corn sirup. Some evidence of carmelization was found after the reaction chamber had been used for numerous conversions. Table I-Conversion TIME Hours 1
I
Figure I-Conversion
hcum
of Starch a t Three Temperatures
The usual charge consisted of 60 cc. of a 6.5" BB. starch suspension. This is somewhat weaker than that used commercially but more suitable for the present problem and apparatus. The introduction of this small volume of cold charge had very little effect on the average temperature of the chamber after a few minutes. The extent of hydrolysis was determined by analyzing samples from the contents of the chamber, which were obtained by opening a sampling valve a t the bottom. Reducing sugar was determined by the method of Munson and Walker (li). The per cent conversion was calculated as follows: Aliquots of the sample were taken and one of them analyzed directly for reducing sugar, the other was treated with hydrochloric acid on a steam bath to complete the starch hydrolysis. The ratio of reducing sugar formed after carbonic acid treatment to that formed after the combined treatment with carbonic acid and hydrochloric acid was taken as the fraction of starch converted. Care had to be taken in the hydrochloric acid treatment not to prolong t h i s unduly. Experimental evidence was obtained showing that prolonged treatment results in a disappearance of reducing sugar which would give conversions considerably over 100 per cent. The time necessary to convert starch completely to reducing sugar, without loss of reducing sugar so formed, varies with the amount of starch initially present. Experimental Results
Table I shows the results obtained a t three temperatures and a t a pressure of 1000 pounds (70.3 kg.) carbon dioxide. These are plotted on Figure 1. It is readily seen that the hydrolysis reaction is profoundly affected by temperature, and that the per cent conversion is practically a linear function of the time. Figure 2 shows the same results, plotting the conversions against the temperature. The samples obtained were generally dark brown in color and could, by a single filtration through Norite, be obtained
156' C.
188' C.
%
%
% 51.2
1z.z
7.1
100
40:s 41.1 63.6 75.3 100
13.2 20.2 26.2
3 4 5
216' C.
35.:
...
1.5 2
100
... ... ...
Table 11-Specific Reaction-Rate Constants (Calculated from Figure 1)
K TIME Hours . . 1
4
Erne
Temperatures
0.86
a
L
of Starch t o Reducing Sugar at Three
-ONVERSION-
2
OO
1437
-
2.3 log
a . -11 a - z
156' C.
186' C.
216' C.
0.0460 0.0360 0.0491 0.0557
0.1490 0.2230 0.2900 0,4060
0.7180
.... .... ....
The results were considered reliable enough to determine whether or not the reaction followed the first-order equation. Hibbert and Percival (2) found that inulin and levan when hydrolyzed with oxalic acid did not follow the monomolecular rate. Table I1 shows the specific reactionrate constants calculated from the slopes of the lines in Figure 1. There is a variation in the values of these constants which makes it still uncertain whether or not this reaction is monomolecular. Figure 1 also shows a line which indicates the rate of hydrolysis using hydrochloric acid a t 140' C. It is seen that this line is somewhat steeper than the one obtained with carbonic acid a t 186" C. and that the rate of reaction is considerably faster. The data on hydrochloric acid conversion were kindly supplied by W. B. Newkirk of the Corn Products Refining Company.
1'
0
/
/
I
16s
7- %.
186
1
2&-
Figure 2 4 o n v e r e i o n of Starch a t Five Time Variations
Conclusions
Starch can be hydrolyzed to reducing sugars by the action of carbonic acid. The rate of hydrolysis depends markedly upon the temperature. It is uncertain whether the reaction is monomolecular. Further work is in progress in which the effects of carbon dioxide pressure and of other gases as well are being studied. Data a t lower temperatures and with varying carbon dioxide pressures and starch concentrations are being obtained. Literature Cited (1) Goodman and Krase, Chem. Met. Eng., 36, 162 (1929). (2) Hibbert and Percival, J . Am. Chem. Soc., 14, 3995 (1930). (3) Jenkinson, Univ. Illinois, B. S. Thesis in Chem. Eng., 1930. (4) Kleiderer and Englis, IND. END.CHSM.,33, 332 (1931). (5) Munson and Walker, J . A m . Chem. Soc., 38, 663 (1906);29,541 (1907).
