T H E EFFECT OF HEATING WITH DILUTE ACIDS, ETC.
395
TARLE V. No.
Scale.
18 19
52.03 56.53 53.70
20
%, Reducing Subtence by Cdlculaiion.
58.40 48.59
52.10
Sime CorreLted
Snme by cu. Sol.
55.83 55.17 56.55
58.81
54.00 51.14
T h e above corrections were based on the supposition th:it 53 divisions of the scale correspond to 5 3 per cent. reducing matter, when the sp. gr. = 1.409, and the percciitqe of water 15. W e may therefore construct the followiiip provisional formulse for estimating the correction to be applied to the reading of the scale when the sp. gr. of the specimen varies much from 1.409. Let a = reading of scale. " w'= corrected reading. '' E sp. gr. of the sample. when the sp. gr. is greater than 1.409, Then a' =a--Sa(e-l.409), a 3a(1.409-e), when E is less than 1.409. and a' I next propose to undertake some investigations t o show the nature and nuniber of the optically active principles present in glucose.
-
+
XLI.-THE EFFECT OF HEATING WITH DILUTE ACIDSAND ~ ' R E A T I N U WITH ANIMAL CHARCOAL, ON THE ROTATORY P O W E R OF GLUCOSE; WITH NOTES ON THE ESTIMATION OF CANES U G A R AND GLUCOSE IN MIXTURE. BY PI~OF. H.W. WILEY. Shaking dilute solutions of glucose or grape sugar with animal charcoal produces a sliiny precipitate. I use the words glucose and grape szignv in their commercial sense. By q2ucose I mean the thick syrup made from corn starch, and by g r q e augur the solid product made from t h e same substance ; by pure glucose I mean the substance present capable of reducing the alkaline copper solution. I mill not take time here to discuss the propriety of these names nor the exact nature of the substances present. I h a w made some experiments t o determine the effect of animal charcoal on t h e rotatory power of glucose of commerce. Following are some of the results obtained. I n each case 10 grms of t h e substance were taken and made u p t o 100 C.C. The observation tube was 200 m.m. in length.
396
TEE EFFECT OF AEATINQ WITH DILCTE ACIDS,ETC. EXPEBIJIENTS.
1.
Reading before addition of coal. . . . . . . . . . . . . . . 52O.00 After shaking with 20 grms c o a l . . . . . . . . . . . . . . 47O.20
Loss,. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4O.80
11. Reading b e f o r b , . ........................... 52O.63 After adding 10 grnis c o a l , . . . . . . . . . . . . . . . . . .50O.28 Loss,. ...................................
1O.35
111. Reading before.. .......................... 52O.63 After addition 4 grnis ivory b l a c k . . . . . . . . . . . . 52O.38
Loss..
.....................................
OO.25
IV. Reading before. ........................... 52O.20 After addition 4 grms ivory b l a c k . . . . . . . . . . . . 5 1 O . 1 3
Loss.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
1O.07
V. Reading before.. ......................... 52O.20 After addition 10 grms ivory black, . . . . . . . . . . 4 8 O . 1 3
Loss..
....................................
2.O.07
From theae figures i t ia certain that a glucose may lose nearly 10 per cent. of its rotatory power when shaken with animal charcoal. This is a matter of great importance when attempts are made to examine commercial syrups with the polariscope. These syrups are usually higlily colored, and require a great deal of bone black aiid lead acetate to make them fit for polariscopic examination. I have not yet tried the action of lead acetate on the rotatory power of glucose. HEATING WITH DILUTE ACIDS.
T h e following readings as well as those in the preceding part of this paper are divisions on t h e cane sugar scale.
THE EFFECT OF HEATING WITH DILUTE ACIDS, ETC.
397
I A glucose gave direct reading..
.............. 53O.70 .......... 52O.96 LOSS, ..................................... OO.74
Heated to 68' with 10 per cent. of its volume of strong hydrochloric acid, reading.
11. Heated same glucose for 50 minutes a t 6B0, reading 50O.76
-
Loss..
.................................... 2O.94 111.
............. ........ _LOSS...................................... 0 O . 3 4
Direct reading another glucose.. 43O.36 Heated for 10 minutes a t 68", with 10 per cent. 43O.02 of its volume strong HCI, reading..
IV. Heated Rame glucose 20 minutes a t 68', reading.
Loss. .................................... V.
,
42O.36
-1 O.00
.... 4O0.16 LOSS.. .................................... 2O.86
Heated same for 30 minutee a t 68", reading..
VI.
...... 39O.26 LORE ..................................... 4O.10
Heated same for one hour a t 6 8 O , reading..
The percentage of reducing substance in the above e rmple before heating with the acid was 62.50 After .................................... 65.58
--
Increase.. ................................ 3.08 Thus a Ions of 4.1 0 on the' cane sugar scale corresponded to a gain of 3.08 per cent. in reducing power. VII. A grape sugar gave direct reading. .......... 40O.83 Heated with one-fifth its volume strong HC1, for 20 minutes a t 6 8 O , reading.. ........... 31O.70
Loss..
....................................
-go. 13
398
THE EFFECT OF HEATING WITH DILUTE ACIDS, ETC.
VIII. A grapo sugar gave direct reading . . . . . . . . . . . 40".00 After heating with one-fifth volume HC1 for 15 minutes a t 68', gave reading.. . . . . . . . . . . . . 32O.82
-~ -
Loss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7O.48 T h e percentage of reducing substance in the above was: Before heating . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69.30 After heating. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 1.50
Gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2.20
T h u s a loss of 7.48 diviaions in rotatory power corresponded only to an increase of 2.20 per cent. in reducing power. It will be seen by inspection of thc foregoing nntnbers that glucosc and grape sugar undergo quite a degree of change when subjected to the process of inversion as it is practiced on cane sugar. This change is sufficiently great t o introduce an appreciable error into the process of estimating cane sugar and glucose in mixtures. CONVERSION O F THE W6IOI.E O F T H E OPTICALLY ACTIVE SUBSTANCES IN GLUCOSE INTO P U R E MONO-ROTATORY GLUCOSE.
I next inade a n attempt to convert the whole of the optically active substaiices present in glucose, into pure glucose, by prolonged heating with dilute sulphiiric acid. T h e conversions were made in a flask fitted with a glass tube about one meter i n Ieiigth. B y this device, vapors arising are condensed and flow back irito the flask. Thus no loss of ~ o l u n i etakes place. T h e flask was a t first heated in a water bath a t 100'. T h e conversion, however, took place so slowly by this method, t h a t I afterwards added enough salt t o the bath t o raise the temperature to 1 0 4 O . T h e sulptiuric acid employed was of 1.25 sp, gr., and was nsed in the proportion of 10 per cent. of the volume of the glucose solution. r , 1he readings wcrc m;idc in a tube longer by one-tenth than half the length of the 2 0 0 m.m., and the result multipliecl by 2. T h e following table contains the resiilts of my work. Nos. 1, 2 atid :< were heated a t 100'. No. 1 for 6 hours, No. 2 for 4 hours, and No. B for 8 hours. Nos. 4, 5 : t i i d 6 were heated for 3 hours a t 102'. h'os. 7 , 8, 9, 10, 11 and 12 were heated for 3 hours a t 101'.
399
THE EFFECT OF IIEArISG WITH DILCTE ACIDS, ETC.
TABLEI. No'
Read i i t g before heating
1 Glucose
before heating
Rending after heating
% Glucose aftenheating
1 2 3 4 5 6 7 8 9 10 11 12
5'2.65 48.40 48.45 43.50 50.26 51.50 52.G5 56.58 51.74 47.70 49.80 40.83
63.20 59.35 58.55 62.50 55. GO 53.50 52.36 54.60 52.36 61.40 58.80 69.93
25.92 27.14 26. 10 24.72 24.18 25.38 25.89 27.36 26.19 25.36 26.02 26.07
81.80 80.0 80.00 79.00 82.00 81.14 83.33 90.10 82.00 82.64 84.00 84.80
111 all cases the samples assumed a decidedly yellowish tint before the completion of the operation, interfering somewhat with the delicacy of the final readings. No. 8 was a sample of glucose made for confectioners' use. If we exclude it wc get the following general results: 1st. T h e percentage of reducing substance obtained is nearly 82.00. 2d. T h e average reading of the cane sugar scale is nearly 25.5 divisions. 3d. If the pure glucose present is mono-rotatory, the specific
8O.85 X 100
rotatory power
e would be e = -2 x 8.2
-54
nearly.
80O.85
is the angular rotation (half sIi3dow) corresponding t o 25.5 divisions of the scale, but the speoific rotatory power of pure glncose for the half shadow polariscope is nearly 50. W e have then here an excess of e equal t o 4. 4th. 'I'his excess is due t o the presence of optically active matter of a higher specific rotatory power than pure glucose, which has not been changed even by prolonged boiling with dilute acid. I conclude, therefore, that it is quite ditlicult to convert the whole of t h e optically active matter into pure nioiio-rotatory glucose. EXAhIINATION O F MIXTURES.
I n t h e examination of mixtures of cane siigar and grape siignr, i t is necessary first t o obtain the direct rending. Afterwards the cane sugar is to be inverted, using a t most not more than ten niinutes for this, and keeping the temperature a t 68'. I t is &ply necessary to heat to 68' aiid then quickly cool.
400
T E E EFFECT OF HEArING WITH DILCTE ACIDS, ETC.
A f t e r inversion t h e temperature is carefully noted and another reading taken. Then b y Clerget’b table the percentage of cane sugar is calculated. This, however, will only be approximately correct. W e next calculate the whole amount of rotation produced by t h e approximate amount of grape sugar present Having determined this, the reading after inversion is t o be corrected for the effect of inversion on the rotatory power of the grape sugar present. T h e average correction, when the heating has been carried just t o 6R’, will be about 2 per cent. of the wholc rotation d u e to the grape sugar. If the process of inversion is carried on for mi hout*, as is t h e practice of some, the correction may aniount to 10 per cent. If the amount of glucose present is very small, this correction can be neglected. B u t if the amount is large, a failure to correct will introduce an appreciable error into the result. If animal charcoal has been used, a correction must be made also for it, depending, as has been shown, upon the amount employed, and also upon some other conditions which are not yet clearly made o u t . It is easy t o see into how grave ai1 error we might fall, h o u l d wc attempt t o intimate directly the percentage of reducing substance present in such mixtures, from its rotatory power. I h a b e shown in a previous paper that the percentage of such reducing substance is not directly but inversely as its rotatory power. T h e error would be equally as grave if the amount of the grape sugar present should be computed by using a factor slipposed to represent the amount of Ruch substanre for each division of t h e scale. Such a method is based upon the assumption that the rotatory power of grape sugar is constant and proportional to the reducing substance present. ;My paper already mentioned shows that tliis assumption is false. SYRUPS.
W h e n we come t o %hesyrups of commerce, the case becomes still more difficult. These syrups are glucose adulterated with so-called cane syrups, i. e., with the drippings and refuse of the sugar refineries. Among the syrups which are commonly used I may mention t h e ‘(Revere ” and the “ Continental.” A “ R e v e r e ” syrup which I examined had a specific gravity of 1.425, and contained 34.5 per cent. cane sugar. A “Continental” syrup had a sp. gr. of 1.415 and 35.7 per cent. cane sugar. It also contained of inverted sugar 32.64 per cent. It is easy t o see how t h e admixture of such syrups with glucose tend t o demoralize the results of the alkaline copper test and mystify the readings of t h e polariscope.
THE EFFECT OF HEATINQ WITH DILLTTE ACIDS, ETC.
401
No wonder that heretofore such egregious blunders have been committed in these examinations. It is only when they are made with a full knowledge of the optical peculiarities of the commercial glucose itself, and of the composition of the cane syrup employed, while a t the same time attention is paid to the changes produced b y inversion and classification, that they tail be relied upon as correct. OBSERVATION TUBES.
In the polariscopic observation of inverted sugars, I use a copper tube silver plated inside and out. I find the most convenient length t o be 110 m.m. This enables the readings t o be made without the trouble of neutralizing the acid. The silver plating of the tube is not necessary, but it makes the working with i t a little cleaner. P u r e copper can be used without any danger whatever of the acid acting on it. I use a tube of thin copper and of small diameter. Such a tube, when filled, quickly takes the temperature of the surrounding air. A few C.C. will fill one of these tubes. I have found by experiment, that when such a tube is filled with a liquid several degrees above or below the temperature of the air, in twenty minutes it will differ by less than half a degree from the temperature. If an ordinary glass tube is employed, it is quite difficult t o say how much time will be required to restore the equilibrium of temperature. My experiments show that it will require from two to three times as long. I also provide this tube with a metallic jacket very conveniently made of a piece of zinc tubing. This jacket is a little less in diameter than the metallic caps of the tube, and is of such a length t h a t when the caps are screwed on, the jacket fits against a shoulder turned on them. The joint is made water-tight by using a rubber packing. This jacket is furnished with three open rings, fitted with short tubes. T h a t in the center carries a thermometer, and those at each end serve as supply or exit tubes for any liquid which we may wish t o pass through the jacket. By simply drilling a hole in the trough of the polariscope f o r the exit tube, the whole apparatus can be placed a t once in position. If now you wish t o make a reading a t a temperature say of 8E0, i t is done in the following way. A large flask or tank placed a t one aide and above the polariscope, and holding several liters of water, is heated t o a temperature of about 92'. By a rubber tube, this is
402
AMERICAN PATEIVTG.
connected, on the prinriple of a syphon, with the observation tribe and its jacket. By means of a pinch cock attached to the exit tube, the hot water is allowed t o flow through the jacket iiiitil t h e thermometer shows the temperature d,esired. I t is hardly necessary t o say that the observation tube must be filled at a temperature near that a t which the reading is to be made, to prevent expansion. If we desire t o make a reading a t O o , correspoiiding to 44" to the left, Clerget, we replace the water by alcohol which is cooled by a salt and ice bath t o -3' or -4". T h e appxratue is then used as before. W e have thus a means of making readings at a n y desired temperature without having to mutilate t h e polariscope, as is done by fitting it with a water bath. I will say, however, that a judicious use of Clerget's principle renders readings a t a given temperature unnecessary, 'LSiey are, hojvever, useful in certain complex mixtures by doing away with certain calculations. I propose next t o extend my investigations to candies and other confections in which glucose enters as an ingredient.
Reports on American and Foreign Patents Relating to Chemistry.
American Patents. Condensed from the Official Gazette of the U. S. Pateut Omce, by A R N O~
~ K H R .
Oct. 5, 2880. 232,889.--Appnrnfus f o r extractins nzetui.front oies.
THURSTON B. HALL.
232,922.-Mnriufurfure of Soap. LOUISBABTET. A compound of soap and mineral oil, with or without the addition of borac ic acid.
JENKIXS. 232,974.- Vnfcnnizedplnsfirronzpourtd. ALFREDB. and CHARLES Use infusorial earth as an admixture to ordinary vulcanized indiarubber. 232,99l.-MefAodand Appnrufrrsf o r obfainifignnznrouia. H A M P. LOI~ENZEN. See Gerinan Patent, p. 302. 232.995.-Frorrss and nppnrnfusforpreparing sncchnmte o f l i m e and obfnining sttgnu. HENRYA. J. MAXOURY. This process hns been sufficiently described in the crirrcnt literature. It is patented in Frnnce and Germany since 1877, nnd extensively adopted in Europe for the recovery of sugar from beet-root molosses.
