I h T D U S T R I A LA N D ENGINEERING CHEMISTRY
January 15, 1930
distillates, and the pycnometer, and which is used to keep everything a t room temperature. Procedure
Standardize the pycnometer a t room temperature, then fill with the distillate a t room temperature and again weigh. Example Temperature of water bath, 17.8" C. Weight of water in pycnometer, 49.8905 grams Weight of 100 cc. water a t 20" C., according to Bureau of Standards alcohol table.. ..................... Twice the foregoing weight of water. . . . . . . . . . . . . . . . Difference. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
99.8230 99.7810 0.0420
Now fill the pycnometer with the alcoholic distillate.
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Let rest a minute or two in the mater bath, when the thermometer should still read 17.8" C., and weigh. Double the weight of the distillate and add the difference, 0.0420 gram which gives the weight of the distillate a t 20" C. Take the alcohol from the Bureau of Standards table. Should the weight of water in the pycnometer exceed the weight of water a t standard temperature, the difference will have to be deducted instead of added. Results are accurate to 0.01 per cent and are more reliable than those obtained in the ordinary manner, owing to the uncertainty of the temperature, which should be accurate to 0.1" C. When dealing with higher percentages of alcohol it pays to dilute "down," so as to obtain a distillate with less than 5 per cent alcohol.
Determination of the Relative Diastatic Powers of Malt' F. C. Silbernagel CEREAL PRODUCTS COMPANY, h ~ A N I T O W O C ,WlS.
H E Lintner value of a malt sample as reported by any laboratory depends on the particular lot of soluble starch used in the test. Hence the probability that two chemists will check each other is contingent upon the same condition, even though the same degree of carefulness and the same technic are employed in both cases. Lintner (3) carefully defined the conditions of carrying out the test and preparing the soluble starch to be used. Since that time many modifications of his method have been proposed, most of which successfully shortened the rather cumbersome original procedure. And the modifications have been modified, until a t the present time almost every laboratory is using a similar yet different method of determining Lintner degrees. Soluble starch according to Lintner, bearing the labels of the most reputable manufacturers, can be purchased at any supply house. It has been the writer's experience that successive lots are sometimes nonuniform, both in content of ready formed reducing sugars and in the ease to which the product lends itself to conversion by malt diastase. This condition has led many laboratories to prepare their own starch, but apparently modifications have been employed here also ( 2 ) . The writer sent four samples of the same malt to four stations engaged more or less in referee work. The results, expressed as Lintner degrees, were 150, 188, 110, and 102. The writer's result was 138. I n cases of controversy the natural tendency of the manufacturer is to accept the report of the station that found 188, and if the purchaser happens to be a client of any of the other laboratories one of two evils ensues, loss of good will or rebates. Malt diastase can liquefy gelatinized starch as well as saccharify liquefied or soluble starch. I n the Lintner test using soluble starch no measure of the first ability results. Commercially, the diastase is generally used to convert gelatinized starch and not soluble starch. Hence, if the liquefying power is appreciably impaired its saccharifying power (as measured relatively by the Lintner test) is of no avail. The liquefying power is not always in the same proportion as the saccharifying power. Lintner (4) proposed a method of evaluating this ability to liquefy. It is the
T
1 Received
August 17, 1929.
purpose of this article to suggest a method incorporating both tests. Diastatic activity is sensitive t o pH control and the value 4.8 has been generally accepted as the optimum. Several laboratories adjust the starch solution accordingly, because it is now known that an unbuffered, so-called neutral, solution is not always neutral so far as its pH value is concerned. For the sake of uniformity we consider pH control as essential, and it should be universally employed in this test. Procedure
Prepare a 5 per cent malt infusion by adding 250 cc. of distilled water to 12.5 grams of the finely ground sample to be tested. Carry out the digestion in a 300-cc. Erlenmeyer flask for 2 hours a t room temperature. During the digestion stopper the flask and shake it continuously on a shaking machine. Meanwhile, prepare the concoction of gelatinized potato starch by weighing 2 grams of the starch into a 200-1212. volumetric flask with a rather wide neck. (The flasks used in phosphorus determinations are recommended.) The flasks previously have been tared. Cover the starch in the flask with about 10 cc. of cold distilled water to form an emulsion-like consistency upon shaking. Pour about 175 cc. of briskly boiling distilled water into the flask and shake vigorously. Then place the flask in a boiling water bath for 15 minutes to insure complete gelatinizing. Cool to room temperature and make up the total weight of the contents to 102 grams. Temper to exactly 21" C. Filter the 2-hour malt infusion until the runnings are brilliant. Add 2 cc. of Walpole's acetate buffer to the flask containing the starch. The starch is quite viscous and a good uniform distribution is essential. Shake well. h'ow add 2 cc. of the filtered malt infusion and allow the reaction to proceed for exactly 30 minutes, at the end of which time arrest the reaction by adding 10 cc. of 0.1 N sodium hydroxide. About 10 minutes after the addition of the diastase solution the gelatinized starch will become liquefied. Until that time almost continual agitation is necessary. I n a wire rack collect a series of test tubes to which have been added 2 cc. of%ehling's solution. After the flask has beenmade up to its mark with distilled water and well shaken,
Ah-.ilLYTICdL E D I T I O S
32
run varying amounts of the solution, for example, 5.5, 5.6, 5.7, 5.8, 5.9, and 6 cc.. into these test tubes from a buret. Effect a good mixture in the tubes and place the rack in a boiling water bath for 20 minutes. Then cool and inspect for the tube showing complete reduction of the copper, using ferrous ammonium sulfate as an indicator or the color change method. Calculate the diastatic value from Ling's formula based on the Lintner scale. However, a few changes in the constants are necessary to accommodate the formula to the concentrations used. According to Ling's ( 1 ) formula,
where A = diastatic power x = cubic centimeters extract in fully diluted starch solution, on the 1-hour reaction y = cubic centimeters needed to reduce 5 cc. Fehling's solution In this case x = 0.5, as a 30-minute reaction was used
5
y = - y', as 2 cc. Fehling's solution was used 2 -
Then A =
800
'Oo0 or A , Y 0.5 X 65 y" ~
.L
If y'
= 53,
A = 151
The foregoing test is carried out under the conditions laid down by Kjeldahl's law of proportionality; also the Lintner scale is preserved. Walpole's acetate buffer consists of 12 cc. sodium acetate (normal), 8 cc. acetic acid (normal), and 80 cc. distilled water. The results in Table I were obtained in this laboratory,
Vol. 2 , s o . 1
using llerck's soluble starch and two different makes of potato starch. All the tests were under p H control. Table I DATE
K I X DO F 1 I A L T
SAMPLE
July 29 July 20 Aug. 5 Aug. 6 hug. 6 .Lug. 8 Aug. 8 Aug. 9 Aug. 11 Aug. 12 .4ug. 1 2 .Lug. 12
Distillers Distillers Distillers Brewers Distillers Distillers Brewers Brewers Distillers Distillers Distillers Brewers
1 2 3 4
3 6 4
7 8 9 4
---DIAZTATIC POWER--Soluble Potato Potato starch 1 2
'Lintner 151 151
I57 119 136 148 120 121 150
...
...
...
Lintner 140 140 145 116 138 138 121 118 140 138 136 116
Lintner
... .. . ... , . . .. . ... ... ...
iik
138 118
All the samples in Table I check fairly well, except sample 3 analyzed on August 6. The soluble starch result is very low, but the potato starch results did not fall accordingly. Whether or not this method is universally accepted, it contains two principles that must be accepted to give a semblance of order in the present chaos. The combination of these two principles appears in no other method. One is p H control. The other is a standard niedium upon which the diastase is to react. Refined potato starch is a far more standard reagent than the soluble starch made from it. L i t e r a t u r e Cited (1) Baker, "Allen's Commercial Organic Analysis," Vol. I, p. 137, Blakis-
ton's, 1909. (2) Brown and Morris, J . Chem. SOL.,450 (1889). ( 3 ) Lintner, Z . p r a k f . Chem., 386 (1886). (4) Lintner, Z. ges. Brnuw., 329 (1903).
Ash and Electrical Conductivity of Sirups and Molasses Derived from Sugar Cane' F. W. Zerban a n d Louis S a t t l e r SEW Y O R KS C G A T R R A D ELABORATORY, 80 SOUTH S T R E E TNEW , Y O R K ,N. Y .
RAPID and accurate conductometric method for the concentration of total solids, namely, around 5" Brix (that determination of ash in raw cane sugars was described is, a t a n ash concentration of about 0.05 gram or less in 100 in a previous paper (7'). The percentage of ash (sul- ml. of solution), the effect of the nature of the non-electrofated ash less 10 per cent) is 0.0001757 (9.13 K 1935 - K 1 ) lytes becomes small. Such a low concentration is therefore where K is the specific conductance x 106 of the sugar so- better adapted for devising a conductoinetric method for lution itself and K1 is that of the solution acidified with determining the ash in sugar products. Honig ( I ) , as well hydrochloric acid, under specified conditions of concentra- as Spengler and Toedt ($), have called attention to this fact, tion. This mathematical expression mill be referred to as and the present writers (8) have confirmed it by experiment. the "conductometric formula." Experimental Procedure The investigation previously reported was extended to I n the conductometric method for detexmining ash in cover various types of sirups and molasses in order to ascertain whether the method would give correct results under raw cane sugars, the writers, following the example of Lange comparable conditions for these products also, or whether and of Toedt, use 5 grams of sugar in 100 ml. Under these conditions, an addition of 5 i d . of 0.25 A- hydrochloric acid it would require some modification. Lunden ( g ) , Sandera (S),and Honig (1) have pointed out t o 200 nil. of the sugar solution more than displaces all the that the depressing effect, on the conductance of the elec- neak acids of the salts contained in the sugar, and the controlytes, of non-sugar non-electrolytes contained in low- ductance measured a t that point lies JT-ell within the straight purity products is greater than that of the same concen- part of the displacement curve. The range of the ash pertration of sucrose in high-purity products. L u n d h and centage in cane sirups and molasses is roughly about 10 times Honig have made use of this fact to judge the quality of sugar as high as in raw cane sugars. While the raw cane sugars products by calculating the ratio between the chemically contain from 0.2 to 1 per cent of ash, cane sirups have about determined ash and the specific conductance, measured a t 1 to 4 per cent, and molasses and barrel sirups about 5 t o high total solid concentration, above 50" Brix. On the other 10 per cent, or a little more. I n order to be able to use again hand, if the conductance determinations are made at a low 5 ml. of 0.25 S hydrochloric acid to 200 ml. of solution, and still have enough acid to more than displace the weak acids, 1 Received M a y 4, 1929 Presented before t h e Division of Sugar it 1%-asnecessary to use only one-tenth of the quantity of Chemistry a t t h e 77th Meeting of t h e American Chemical Society, Columbus material employed in the case of raw sugars. For this reason Ohio, April 29 t o M a y 3, 1929
A
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