ing of sugar solutions of high concentration. That sugars and their degradation products are able to expel volatile or unstable acids a t temperatures below the charring point is of particular interest t o analysts when called upon t o determine the anions present in plant juices, in articles of food, or in insecticides b y methods which involve evaporation of sugar-containing solutions preparatory to extraction or to incineration.
IMPURITIES IN WHITE SUGARS
Method of Studying Loss of Anions
The loss of anions from certain salts in concentrated sugar solutions a t temperatures between 107" and 176" C. was studied by analyzing samples taken a t definite temperatures during hard candy tests (2) made with a standard low-ash sugar t o which were added known quantities of the salts: In each case the candy test was started as usual, using the salt being studied, 227 grams of the standard sugar, and 90 cc. of distilled water. As soon as the sirup boiled vigorously (107' C.), a sample was removed with a tablespoon and poured into 50 cc. of water. The boiling sirup was then covered with a watch glass until 15 minutes from the start of the test. After remoLing tee glass, the siru was stirred as usual and sampled at 135 , 155 , and 176" C. Each sample was immediately quenched in 50 cc. of distilled water in which it was dissolved as quickly as possible after completion of the test and, when cooled, diluted to 100 cc. with water. After analysis of the solution for the anion of the salt used, the ratio of the quantity found to the total solids (T. S.) in the solution was calculated and, for convenience, multiplied by 103. Because of the decreases in the volume of the sirup resulting from the successive sampling, the sirups attained a temperaJ. A. AMBLER ture of 176" C. in a shorter time than in the regular candy Bureau of Chemistry and Soils, Washington, D. C. test. Therefore the resulting candies are not quantitatively comparable with any others previously described in this series of articles but constitute a new group, the members of HE study of the effects of different salts which are comparable among themselves. The fact that this on sucrose during the "barley" or hard study was directed toward the effect of the sugar on the noncandv test, reDorted bv Ambler and Bvall sugar rather than toward the inversion and caramelization of in the preceding paper 01this series (9),led to the classification the sugar, warrants the change of technic. The results obof salts into three groups. The opposite effects of the salts tained indicate qualitatively the trend of the reactions in the of t h e first two of these groups on t h e inversion and discoloraregular candy test and in the evaporation of saccharin juices tion of sucrose were explained and sirups. by the assumption, arrived It was found that a hard at from qualitative evidence candy satisfactory for experiNo chlorides, iodides, or sulfates, when derived from sodium nitrite mental purposes can be made present alone, are lost from boiling sufrom commercial dextrose as and sodium acetate (8), that crose solutions at temperatures below the only sugar present, using double-decomposition reac176" C. During the evaporation of sutions are set up a t higher the regular technic with 227 grams of commercial anhytemperatures b e t w e e n t h e crose or of dextrose solutions by boiling, salts and the sugar, w h e r e drous dextrose and 100 cc. there is a loss of sulfites between 107" o f w a t e r . To a s c e r t a i n the sugar and its degradaand 176" C.which may total 100 per cent. whether the action of a reduction products act as nonvolaIf sulfates are present, they may also be ing sugar (dextrose) on the tile acids. With the salts of lost. Fluorides are lost in part from hot salts is different from that of the first group such reactions t h e nonreducing sugar would liberate the ions of sucrose and dextrose solutions even besucrose, candies were made acids which are not volatilized fore the solutions reach the temperature from dextrose Kith some of during t h e test and hence of 107"C. Sugars in solution are capable the salts. KOdifferences atpromote i n v e r s i o n and inof reacting as nonvolatile acids at higher tributable t o the presence or hibit discoloration and, with temperatures and of causing a loss of absence of a reducing group many salts of t h e s e c o n d in the sugar were detected. group, the ions of acids rrhich volatile and unstable acids present in the The salts s t u d i e d w e r e are volatilized or decomposed solution. sodium c h l o r i d e , calcium into volatile anhydrides durc h l o r i d e , potassium iodide, ing the test, leaving behind sodium sulfate, sodium sula n i n c r e a s i n g alkalinitv fite, and sodium fluoride. The chlorides and sulfates were which, in turn, lnhibits inkersion and promotes discolorashown in the previous paper (2) to belong t o t h e first, or intion. Further basis for this assumption was obtained from verting, group of salts, and sodium sulfite to t h e second, or a quantitative study of the loss of anions during t h e boildiscoloring, group. Potassium iodide is to be classed with 1 Previous papers in this series appeared in IND. ENQ.CHEY., Anal. Ed., thechlorides and sulfatesinthefirst groupandsodiumfluoride 3, 136, 339, 341 ( m i ) , 4 , 3 4 , 3 m , 379 (1932), 7, 168 (1935); end in IND. with the nitrites, acetates, and sulfites in the second group. ENO.CHEM.,27, 30 (1935).
IX. Loss of Anions from Certain Salts during Evaporation of Concentrated Sugar Solutions'
1266
NOVEMBER, 1936
INDUSTRIAL AND ENGINEERING CHEMISTRY
The characteristics of a hard candy containing fluoride are shown in Table I in comparison Kith those of a candy made from the standard sugar. Both candies, having been made by the regular hard candy technic, are comparable with those previously described. T.4BLE
I.
L4S.iLYsIS O F
BARLEYC A S D Y FL~ORIDE Standard
CONTAIKISQ SODIChl
+
Standard 0.200 G. Pure N a F
Chlorides, Iodides, Sulfates From the analyses for the chloride ion (Table IIA and B ) , it is evident t h a t there is no loss of chloride u p to 176" C. Losses of chlorides which occur during ash determinations (4), therefore, take place at higher temperatures and are to be attributed either t o pyrolytic displacement by other less volatile anions or to reactions during the charring and incineration of the organic substances, resulting in the production of chlorine or of volatile chlorine compounds. The same holds true for iodides (Table IIC) and for sulfates (Table IID) even in alkaline solution (Table I I E ) and in the presence of reducing sugar (Table IIF).
method was abandoned in favor of the gravimetric method of determining sulfate and total sulfur after oxidation to sulfates, the difference representing the sulfites (9). From the results obtained with sulfates alone (Table IID, E , and F ) , we would expect that there n-ould be no loss of sulfates. However, in the presence of sulfites, Table 111-4 and C, there is a n apparent and appreciable loss. It is possible that in Table IIIA the apparent complete loss of sulfate might be due to the peptization of the small quantity of barium sulfate by degradation products of the sugar acting as protective colloids. When additional sulfate was introduced to counteract this possible effect (Table IIIB), no loss of sulfate was indicated, but the larger amount of sodium sulfate retarded the rate of loss of total sulfur and of sulfite, indicating that the course of the reaction had been changed. The ioss of sulfate is not due to alkalinity as is shown in Table IIE. Probably it is caused, if not by peptization of the barium sulfate, by some reaction of the sulfite ion itself. T h a t reducing sugars react under other conditions with sulfites a t about 130" to 135" C. has been known for some time and studied by Hagglund et al. (5) and by hlarusawa, Saito, and Uchida (6) among others, who report the formation of thiosulfate and polythionate ions and oxidation of the sugar. At present it is impossible to investigate the course of such a type of reaction in the candy test because of analytical difficulties, but the apparent loss of sulfate in the dextrose sirup (Table IIIC) might m l l indicate some type of complex reaction in addition t o any loss of sulfite by volatilization as sulfur dioxide. The loss of sulfite ion during the test is established, although t h e manner in which it disappears must remain undetermined for the present.
TABLE 11. EFFECTS O F BOILINQ ON
V.4RIOUS S.4LTS IS SUCROsE SOLKTTIOSS -.4. Sodium Chlorides-7 -D. Sodium SulfateeSampling 103 X Sampling 103 x temp. C1-b T. S . Cl-:T. S. temp. SOaf T. S. SOa:T. S. Cl Mg. Grams C. .Mg. Grams Start ... ,. 1.33 Start .. .. 1.24 (calcd.j (calcd.) 107 21.6 17.5 10.33 1.32 1.23 107 13.65 135 28.0 22.5 1.24 15.14 1.32 135 20.03 25.0 20.4 1.23 1.32 155 155 19.33 14.66 176 43.4 34.0 13.35 1.28 176 17.02 1.27 --B. Calcium Chloride- C -E. Alkaline Sodium Sulfateg107 26.5 20.0 1.33 Start .. .. 1.24 135 23.7 18.1 1.31 (calcd.) 155 23.4 17.3 1.35 107 21.6 17.0 1.27 176 41.0 31.8 1 29 135 24.2 19.3 1.25 155 22.6 17.9 1.26 176 48.6 38.1 1.28 C. Potassium Iodided--. F . Sodium Sulfate and Dextroseh 1-b 103 x I-:T. S. Start ... ... 1.68 Start .. .. 1.34 (calcd.) (calcd.j 107 22.84 13.50 1.69 107 21.2 15.8 1.34 1.74 135 21.6 15.6 135 29.5i 17.00 1.38 1.71 155 31.73 18.51 22.4 16.1 155 1.39 176 35.91 20.76 1.73 176 20.8 15.8 1.32 a 0 500 gram c . P. NaCl 227 grams sucrose, 90 cc. water. b Determined by Mohr's( method for chlorides ( 1 , 7). c 0.500 gram anhydrous reagent-grade CaCl?, 227 g r a m sucrose, 90 cc.
.
~~
1267
Fluorides Sodium fluoride is not a normal constituent of purified white sugars, but the use of fluoride and fluorine compounds as insecticides for fruit crops makes the action of saccharin juices on sodium fluoride important to those Tho undertake the development of new methods for determining small quantities of fluorine in or on foodstuffs. As shown in Table I, sodium fluoride behaves in the candy test like sodium nitrite, acetate, or sulfite in that it yields a dark candy and inhibits inversion. When this barley candy was analyzed for fluorides, it was found to contain only 312 parts per million of fluorine whereas 399 parts per million had been added t o
7 -
h 0.500 gram anhydrous Na:SOd, 227 grams commercial anhydrous cerelose (92.4Y0j, 100 cc. Mater.
Sulfites The loss of sulfite ion is strikingly shown in Table 111. Since i t was impossible to prevent oxidation of a portion of the sulfite to sulfate during the tests and analyses, a partition of the total sulfur into sulfur trioxide and dioxide was undertaken. The determination of sulfur dioxide in the samples by titration with iodine ( 3 ) gave a poor end point and, in the samples taken a t 155" and 176" C., yielded high results because of the presence in these samples of iodine-absorbing degradation products of the sugar. Therefore the volumetric
TABLE 111. EFFECT OF BOILIXG ON SODIUM SULFITE IX SUCROSE SOLUTIONS 103 x io* x 101 x
Total SOs: SO*: T. S. S:T. 9. T. S. T. S . Grams 8 . Sodium Sulfiteb 8.8 13.3 16.9 1.50 107 25.4 0.52 0.78 15.1 21.7 1.21 26.2 7.3 0.34 0.70 135 7.7 19.2 0.50 0.0 0.00 0.40 155 9.6 176 8.9 0.0 7.1 25.5 0.35 0.00 0.28 B. Sodium Sulfite and Sodium Sulfatec 40.0 42.0 22.4 4.13 1.79 1.87 107 92.5 70.0 32.0 30.4 135 16.9 4.14 1.89 1.80 155 75.6 35.2 32.3 19.7 3.84 1.78 1.64 23.9 22.1 3.06 67.6 38.0 1.72 1.07 176 C. Sodium Sulfite and Sodium Sulfate with Dextroseci 31.6 32.3 3.93 107 72.0 18.3 1.73 1.76 29.6 23.0 18.8 1.57 1.22 135 58.4 3.11 155 27.2 28.0 -0.6 16.7 1.63 1.68 -0.04 176 31.6 31.6 0.0 21.4 1.48 1.48 0.00 Total sulfur determined by oxidation with iodine and precipitation as BaSOd. Sulfates determined gravimetrically as BaSO4. Sulfites determined b y difference (3 9). Oxjdation with bromine water gave identical results. b Fresh soludon of 0.20 gram SO1 in water (by iodine titration), neutralized with calculated quantity of NaOH, diluted with distilled ivater t o 90 cc., and added to 227 grams sucrose. C 1.000 gram anhydrous NaZSOn, 0.500 gram anhydrous SazSO4, 227 grama sucrose 90 cc. water. d l.Ob0 gram anhydrous NagSOa, 0.500 gram anhydrous Ka&OI, ,227 g r a m commercial anhydrous cerelose (92.4%), 100 cc. water. T h e sirup began to darken soon a f t e r boiling started, during the period t h a t i t u'as covered with the watch glass. Sampling Total Temp. as S O P
C.
Q
Mg.
SOP
SO*"
Mg.
Ye.
the sugar. There was thus a loss of 21.8 per cent of fluorine. Table IV shows that a portion of this loss took place before t h e solutions boiled, or below 107" C. The maximumerror in the fluorine determinations is *8 per cent. Although the losses found between consecutive samples were usually less than this, the facts that in every case but one a loss was indicated, that in this one exception the difference between the values found was practically negligible, and that the over-all losses are a t least twice the maximum experimental error, preclude the possibility t h a t the losses are not real and indicate that both sucrose and dextrose readily expel fluoride ion from hot solutions. The fact that t h e loss is very little above 135" C. may possibly have a n explanation in that equilibria may be set u p with the basic fluoride remaining, or complex fluorine compounds may be formed which remove fluoride ion from the attack of the sugar but retain fluorine in the sirup. TABLEIv. EFFECTS O F BOILING O N SODIUM FLUORIDE IN SUCROSE SOLUTIONS Sampling Temp.
F
T. 5.
c.
Mg.
Gams Sodium Fluoridea
O
VOL. 28, NO. 11
INDUSTRIAL AND ENGINEERING CHEMISTRY
1268
108 X F;T.
S. Loss %
Sodium Fluorideb
Sodium Fluoride and Dextrose C 0.432 (calcd.) Start 107 6:06 l2:7 0,398 7:s 135 6.29 17.3 0.364 15.7 155 6.94 19.6 0.354 18.1 176 7.33 21.1 0.347 19.7 a 0.200 gram pure NaF, 227 grams sucrose, 90 cc. water. The sirup darkened at about 160' C. b 0.400 gram pure NaF, 227 grams sucrose, 90 cc. water. The sirup darkened at about 160' C. C 0.200 gram pure NaF 227 rams commercial anhydrous cerelose (92.4%*,), 100 cc. water. Thl nirup ckarkened at 158' C.
, Acknowledgment T h e author is indebted t o S.Byall of the Carbohydrate Research Division, Bureau of Chemistry and Soils, for the analyses of the two candies given in Table I, to R. U. Bonnar of the Food Division, Food and Drug Administration, for the fluorine analysis of the candy containing sodium fluoride. D. Dahle of the Food Division made the fluorine analyses on the experiments from which the data in Table IV were obtained, by a method developed and to be published by him.
Literature Cited (1) Ambler and Byall, ISD. Eso. CHEW,Anal. Ed., 4, 379 (1932). ( 2 ) I b i d . , 7, 168 (1935). (3) Ambler, Snider, and Byall, Ibid., 3, 339 (1931). (4) Browne and Gamble, Facts About Sugar, 17, 552 (1923). (5) Hiigglund et ai., Svensk Kern. Tid., 41, 8, 55 (1929) ; Ber., 62, 84, 437, 2046 (1929); 63, 1387 (1930); 68, 822 (1935); F i n s k a Kemistsamfundets M e d d . , 39, 49 (1930). (6) Marusawa, Naito. and Uchida, Mem. R v o j u n CoZZ. Eng., 1, 351 (1929) (7) Mohr, A n n , 97, 335 (1856) (8) Pucherna, 2.Zuckerznd. EechosZouak. Rep., 5 5 , 144 (1930-31). (9) 2240 (Feb 28, 19321, .. . . Saillard. Czrc. hebdo. fabr. sucre, SUPPI. 2244 (March 27, 1932). I
RECEIVED September 3, 1936. Contribution 133 from the Carbohydrate Research Division, Bureau of Chemistry and Soils.
Permeability of c
U
A
'
l
Lacquer f-ilms to Moisture ROBERT I. WRAY AND A. R. VAN VORST Aluminum Company of America, New Kensington, Pa.
Clear lacquer films of a variety of commercial compositions show considerable variation in permeability to moisture. In general, the lacquer films increase in moisture resistance with age; this behavior makes the time of testing the films after their preparation an important factor in interpreting the data. The permeability of the films has also been determined in contact with liquid water; the behavior in this test is not entirely consistent. Baking appears to increase the moisture resistance of some of the films, especially after aging.
R
ESULTS of the investigation of the permeability of oil and varnish-base paint films to moisture were published in previous papers (1, 6 ) . Data on the permeability of clear lacquer films are presented in this paper. Gettens and Bigelow (d), the Hercules Powder Company (S), and Wing (4) have already reported some work in this field; these investigations determined only the initial permeability of the lacquer films. The effect of aging of the films, discussed in the present paper, is also important. In general, the permeability was found to decrease Kith the age of the films, in some cases in a striking manner. This fact is an important consideration in comparing and interpreting tests on lacquer films. The measurements are of practical interest because the use of clear lacquer coatings with good resistance to moisture penetration is necessary for many applications. It is also important, as a rule, that the lacquers maintain good flexibility as well as moisture resistance, even when exposed indoors for extended periods.
Effect of Age on Permeability of Films A series of tests was made to determine the relative moisture resistance of several types of commercial lacquers : The lacquer films were applled to amalgamated tin plate panels bv minninz. as Dreviouslv described (6). After the films were dried for various periods,'they were stripped from the panels and cemented to shallow Petri dishes containing activated alumina. After weighing, they were placed in a cabinet maintained at 95 per cent humidity and 80" F. (26.7' C.). The dishes, with films attached, were weighed every 24 hours to determine the amount of moisture passing through the films and absorbed by the activated alumina. In applying the different lacquers, they were reduced to a uniform viscosity (where possible) of 0.85 poise. Two of the lacquers tested had viscosities lower than this when received and
