THE PREPARATION OF ACID-FAST 
 
 CARAMELS 
 
 HY 
 
 nONAJLD FYFE BOWEY 
 
 THESIS 
 
 FOK THK 
 
 DEGREE OF BACHELOR OF SCIENCE 
 
 IN 
 
 ('BEMISTRY 
 
 CUJLLEGE OF LIBERAL ARTS AND SCIENCES 
 
 UNIVERSITY OF ILLINOIS 
 
 1922 
 
Digitized by the Internet Archive 
 in 2016 
 
 https://archive.org/details/preparationofaciOObowe 
 
I92Z 
 
 _BS7 
 
 UNIVERSITY OF ILLINOIS 
 
 May 34 
 
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TABLE OF CONTENTS 
 
 Page 
 
 ACKNOMiEDGIiENT 
 
 I. INTRODUCTION 1 
 
 II. HISTORICAL 3 
 
 III. EXPERIMENTAL 7 
 
 IV, AN INVESTIGATION OF THE 
 
 PURIFIED CARAMELS. 19 
 
 V. CONCLUSIONS 33 
 
 VI. BIBLIOGRAPHY 33 
 
ACKN0?,'LEDG11ENT 
 The writer wishes to express 
 his sincere appreciation for the 
 inspiration and helpful suggestions 
 from Dr. George D. Beal, under whose 
 supervision this investigation was 
 carried out. 
 
- 1 - 
 I 
 
 INTRODUCTION 
 
 Caramel is, as the name indicates, hurned or carbonized 
 sugar, used primarily in the food industries whenever a rich brown 
 color is required, and when made by the heating of cane sugar 
 without chemical reagents, has a secondary value as a flavoring 
 agent in confectionery, baker's goods, etcetera. Convenience of 
 preparation and the fact that caramel is a representative of the 
 harness class of vegetable colors, combine to lend popularity to 
 this substance. 
 
 The investigation of carauTiels has attracted the sporadic 
 interest of many chemists since the beginning of the nineteenth 
 century. There is perhaps no subject in food chemistry that has 
 been given such w'ork and throught in all the leading countries 
 and has yielded such .fruitless returns as the subject of caramiels. 
 
 The experiments carried on by these earlier chemists, however, 
 have been along a purely scientific and theoretical basis. They 
 were merely interested in the chemistry of caramels. The first 
 half of the nineteenth century was spent largely on the analytical 
 side of the subject and finally gave way to the mors important 
 investigation of the synthesis of caramels. 
 
 The purpose of this paper is somewhat different from most of 
 the literature found on this subject. The main problem deals with 
 the preparation of a caramel that will satisfactorily comply with 
 all the tests and specifications required by up-to-date users and 
 
 will be sufficiently economical in preparation to compete with 
 
- 3 - 
 
 commercial caraunels on the market today. 
 
 In discussing the literature available on the subject we will 
 mention orily briefly the works of the earlier chemists. The his- 
 tory of the manufacture of caramels will be disucssed more thor- 
 oughly, the uses of the colors and finally why an acid-fast caramel 
 has been demanded for commercial consumption. 
 
 The second part of the paper takes up the preparation of an 
 acid-fast caramel by the catalytic distillation of commercial 
 glucose and its purification. The paper is concluded with an 
 investigation of the purified caramel. 
 

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- 3 - 
 
 II 
 
 HISTORICAL FACTS. 
 
 Caramel is regarded as an intermediary compound formed in the 
 
 dry distillation of sugars. It may be obtained from the various 
 
 produce 
 
 sugars of commerce by heating them to the temperature necessary to/ 
 the greatest quantity of soluble coloring-matter. Different temp- 
 eratures are required for the carmeilization of different sugars 
 and the compounds obtained from these sugars differ a great deal 
 in physical and chemical properties. (it was also noticed during 
 the course of the experimental work that these same properties 
 were changed considerably by the use of different methods for the 
 purification of the caramel.) 
 
 The first mention of this subject is in an original article 
 
 ( 1 ) 
 
 by Peligot . He mentions that caramel was used as a coloring 
 
 and a therapeutic agent at this early time and gave it an empirical 
 
 (3) 
 
 form\ila of C 4 aH 3 60is* Volckel working a few years later was able 
 to throw a little additional light on the subject but came to an 
 entirely different conclusion regarding the structure of the com- 
 pound. He assigns to caramel the emoirical formula C^gHgOg, 
 
 (3) 
 
 In 1858, five years later, Gelis published an article worth con- 
 sidering. He made three distinctions in the compounds in caramel, 
 namely; carmelene, caramel in, and caramel ane. These showed 
 differences in solubility which resulted probably from increased 
 molecular weights. He gave his compound the formula CigHie09* 
 
 Gelis was the first man to notice the ■dissimilarity between the 
 physical and chemical properties of caramel formed from glucose 
 
and from sucrose. 
 
 - 4 - 
 
 (4) 
 
 In the dry distillation of sugars Trillat shov;ed that there 
 
 were other products simultaneously evolved, such as formaldehyde, 
 
 henzaldehyde , acetic acid, acetone, phenolic compounds, etc. The 
 
 (5) 
 
 latest paper on the chemistry of caramels by Cunningham and Doree 
 covers a large field ori the derivatives and reactions of this 
 compound. 
 
 The theoritical and structural investigations of caramels, 
 
 however, do not bear as directly on the problem of this paper as 
 
 do the investigations on the preparation and manufacture of cara- 
 
 (6) 
 
 mels. In ISIO, J. J. Kazewinkel published a method for the manu- 
 facture of caramels by heating molasses with 15'^ of water at 135®C. 
 for 5-10 hours. He states in his paper that a higher temperature 
 shortens the time of caramel Izat ion but necessitates mors careful 
 control. He also advises that an acid caramel should be neutral! zee 
 before using. It is evident from the time necessary to prepare 
 the sugar color from molasses that this procedure could not be 
 
 satisfactorily used in the commercial preparation of this compound. 
 
 (7) 
 
 A few years later A. Herzfeld prepared a caramel by heating 
 an 80^ invert sugar syrup in an oil bath. He found that the 
 period of caramel izat ion could be greatly reduced by the addition 
 of ammonia from time to time, although he v/as not certain just 
 what the effect of this catalyst had upon the reaction. The temp- 
 erature was raised quickly to 170®-80°C. and the carai^isl so made 
 complied with all the specifications required at that time. One 
 

- 5 - 
 
 great advantage of this compound was the lack of the bitter taste. 
 The discovery of the catalysing action of ammonia in the caramel- 
 ization of sugars was a long stride forward in the commercial 
 manufacture of sugar colors. 
 
 (e) 
 
 Another acfirance was made in caramel manufacture when L. Eriant 
 in 1913 stated that a desirable compound to be used in the coloring 
 of beers should not suffer any change in tint when treated v;lth a 
 0.5^ solution of tartaric acid. He prepared his caramel by heating 
 glucose with the addition of ammonia and its salts. This is the 
 first nublishwil record v/e have of an acid test for caramels, Erste 
 
 ( 9 ) 
 
 Wiener Export in 1919, published an article on the preparation of 
 caramels from sugars in the presence of 0,03-0,1^ of its weight of 
 acid, a temperature of 150 degrees C. being employed. He does not 
 state which acid was used but it is supposed that one of the more 
 coi^on Inorganic acids as hydrocliloric, nitric, or phosphoric was 
 employed. The presence of this small amount of acid was sufficient 
 to greatly accelerate the reaction with the formation of a very 
 satisfactory caramel. 
 
 A few papers have been published within the last two years on 
 the manufacture of caramels but they discuss only ordinary methods 
 of preparation. The market for commercial caramels has increased 
 gradually during the past decade, especially since the passing of 
 the Volstead Act. Although this compound was used to some extent 
 in the coloring of beers, wines, and whiskeys, its principle use 
 at the present time is in the soft drink industry. The bakers 
 
- 6 - 
 
 and candy manufacturers have also found it essential as a coloring 
 agent . 
 
 ^Vith this marked increase in the caramel industry, competition 
 among the manufacturers became fairly keen. An eastern concern 
 succeeded in manufacturing by a secret process a caramel that they 
 advertised as being acid-fast. They capitalized this test until 
 the majority of caramel users in the country would accept only an 
 acid-fast caramel. The test they specify is as follows: Sixty 
 
 grains of the concentrated caramel are dissolved in 350 cc. of hot 
 water. If one-half of this volume on boiling with 1 drahra of com>- 
 mercial hydrochloric acid v/ill remain clear for 30 minutes with no 
 visible loss in tinctorial strength, it is said to be acid-fast. 
 Caramels manufactured by ordinary processes will not stand this 
 test. 
 
 It has been proven conclusively by investigators that ordinary 
 sugar colors will make a very satisfactory coloring agent for soft 
 drinks, bakers supplies, and candies, but the acid-fast caramel 
 has been advertised to such an extent that it has practically be- 
 come the standard of the industry. The preparation of a compound 
 that will satisfy this test is explained in detail in the experi- 
 mental part of this paper. 
 
- 7 - 
 III 
 
 EXPERILIENTAL PART 
 
 In the commercial manufacture of caramels the glucose is 
 
 a 
 
 heated in large cast iron kettles hy./coal fire. It is very evident 
 that under these more or less crude conditions a constant temijer- 
 ature is hard to maintain. Rather than adopt a similar method 
 in the laboratory for the preparation of this compound it was 
 deemed advisable to use apparatus which would allow a much closer 
 control of the caramel iz at ion process. The apparatus used con- 
 sisted of a one-liter Pyrex flask supported in a bath of cotton- 
 seed oil. The oil bath fitas kept at a constant temperature within 
 the range of a few degrees, and served as a very convenient means 
 of distributing heat. 
 
 Pure sucrose was tried at first, but it was found to be an 
 expensive proposition. Commercial glucose was next obtained and 
 was analysed optically for its purity. It contained 18.68*^ water 
 and 85.65'^ dextrose. The apparent percentage of the dextrose was 
 somewhat high due to impurities that were not removed from the 
 sugar solution. Several preliminary batches were run to establish 
 some definite method of procedure which would give the desired 
 results. A very satisfactory method of cooking is as follows: 
 
 100 grams of glucose are melted in 35 cc. of water. The empty 
 pyrex flask ts lowered into the oil bath and the bath heated to 
 the temperature desired. The melted glucose is then quickly 
 poured into the flask and the time noted, a constant temperature 
 
- 8 - 
 
 bsing held throughout the entire operation. At the finish of 
 caramel ization 500 cc. of distilled water is added and the mixture 
 allowed to stand for half an hour to dissolve the hardened caramel. 
 The solution is then filtered through weighed Gooch crucibles to 
 remove the char and other insoluble matter. Char sticking to the 
 inside of the flask is removed by warming with a 10^ solution of 
 sodium carbonate. 
 
 The caramels prepared by the above method were tested for: 
 acid-fastness, tinctorial strength, and percent of char, the three 
 main tests on which a caramel is based. The acid test employed 
 in these experiments was not exactly the same as explained in the 
 introduction of this paper. The test was carried out by diluting 
 25 oc. of the filtered caramel solution with 50 cc. of distilled 
 water, adding 5 cc. of 6 N. hydrochloric acid and boiling the 
 mixture in a small beaker. This test gave comparative results 
 which were entirely satisfactory. Ordinary caramels broke down on 
 10 to 15 minutes boiling with this concentration of acid but the 
 acid-fast compounds remained perfectly clear on prolonged boiling. 
 The formation of the murky solution and the dark brown precipitate 
 on boiling the ordinary sugar colors with the acid is probably due 
 to the hydrolyzing action on the unchanged sugar. If this state- 
 ment were true it is obvious that an acid-fast caramel could be 
 pfepared by converting all the glucose into pure caramel. 
 
 The caramel was tested for tinctorial strength by diluting 
 5 cc. of the filtered compound in a 100 cc. measuring flask. This 
 diluted solution was then tested in a standard colorimeter for tint 
 
- 9 - 
 
 Th3 tinctorial numbers used in the follovdng tables can only be 
 used for comparative purposes, the higher numbers denoting a higher 
 tint. 
 
 The first experiment consisted of determining which temperature 
 and time of cooking would yield the best caramel. This was per- 
 formed by cooking a series of batches keeping an accurate record 
 of the time of the heating with the temperature constant, and test- 
 ing the resulting caramel for acid-fastness, tinctoria.! strength, 
 and percent of char. The weight of char was not obtained accurately 
 on the analytical balance because these figures were only needed 
 as a means of comparison. In the first series of batches 100 grams 
 of glucose were used in each batch without the addition of a 
 catalyst. 
 
 
 Time 
 
 Temperature 
 
 ®c. 
 
 ^ of Char 
 
 Tinctor- 
 ial no. 
 
 Acid 
 
 Test 
 
 35 
 
 min. 
 
 310 
 
 3.68fo 
 
 23 
 
 8 
 
 min. 
 
 30 
 
 n 
 
 210 
 
 3.0lfo 
 
 36 
 
 10 
 
 It 
 
 35 
 
 It 
 
 310 
 
 3. 34^0 
 
 35 
 
 10 
 
 II 
 
 40 
 
 ti 
 
 310 
 
 3.39fo 
 
 34 
 
 10 
 
 n 
 
 45 
 
 ti 
 
 210 
 
 2.53fo 
 
 33 
 
 10 
 
 n 
 
 50 
 
 It 
 
 210 
 
 
 39 
 
 10 
 
 N 
 
 65 
 
 II 
 
 310 
 
 4. OOfo 
 
 36 
 
 17 
 
 II 
 
 60 
 
 It 
 
 310 
 
 6. 45fo 
 
 33 
 
 15 
 
 n 
 
 65 
 
 It 
 
 310 
 
 5.18f. 
 
 36 
 
 15 
 
 II 
 
 70 
 
 n 
 
 310 
 
 7,84fo 
 
 40 
 
 18 
 
 II 
 
- 10 - 
 
 Time 
 
 Temperature 
 
 ®C. 
 
 ^ of Char 
 
 Tinctor- 
 ial no. 
 
 Acid Test 
 
 35 
 
 min. 
 
 320 
 
 3.00fo 
 
 25 
 
 13 
 
 min 
 
 30 
 
 n 
 
 330 
 
 6.67fo 
 
 36 
 
 15 
 
 It 
 
 35 
 
 n 
 
 330 
 
 5.59/0 
 
 38 
 
 15 
 
 It 
 
 40 
 
 n 
 
 330 
 
 3.07/ 
 
 26 
 
 13 
 
 II 
 
 45 
 
 tt 
 
 330 
 
 4.78/ 
 
 31 
 
 16 
 
 Tl 
 
 50 
 
 n 
 
 330 
 
 7.43/ 
 
 35 
 
 16 
 
 IT 
 
 55 
 
 n 
 
 330 
 
 6.61/ 
 
 33 
 
 15 
 
 It 
 
 60 
 
 n 
 
 330 
 
 4. 60/ 
 
 55 
 
 15 
 
 Tt 
 
 65 
 
 n 
 
 330 
 
 7.18/ 
 
 38 
 
 16 
 
 It 
 
 70 
 
 Tt 
 
 330 
 
 8.30/ 
 
 43 
 
 17 
 
 II 
 
 35 
 
 Tt 
 
 330 
 
 3.15/ 
 
 36 
 
 13 
 
 It 
 
 30 
 
 IT 
 
 330 
 
 3.36/ 
 
 33 
 
 13 
 
 IT 
 
 35 
 
 n 
 
 330 
 
 5.19/ 
 
 36 
 
 15 
 
 It 
 
 40 
 
 Tt 
 
 330 
 
 4.95/ 
 
 3T 
 
 15 
 
 n 
 
 45 
 
 n 
 
 330 
 
 6.31/ 
 
 36 
 
 15 
 
 IT 
 
 50 
 
 11 
 
 330 
 
 7.55/ 
 
 38 
 
 16 
 
 TT 
 
 55 
 
 TT 
 
 330 
 
 7.85/ 
 
 41 
 
 18 
 
 IT 
 
 60 
 
 TT 
 
 330 
 
 6.19/ 
 
 38 
 
 17 
 
 TT 
 
 65 
 
 IT 
 
 330 
 
 5.50/ 
 
 36' 
 
 15 
 
 TT 
 
 70 
 
 n 
 
 330 
 
 8,55/ 
 
 43 
 
 16 
 
 TT 
 
- 11 
 
 It was perfectly apparent from the above .tests that an 
 acid-fast caramel could not be prepared by this simply dry distilla- 
 tion of the glucose. Not only did the resulting caramel break dovm 
 on boiling with the acid but the tinctorial strength was far too 
 low for the length of time required in the cooking. It was also 
 noted that the caramels containing a higher percent of char gave a 
 higher tinctorial number and remained clear longer in the acid. 
 
 Previous investigators on the preparations of caramels found 
 that by the addition of a fairly dilute solution of sodium carbon- 
 ate during the caramel izat ion process the color strength would be 
 greatly Increased. Four batches were prepared by adding 100 cc. 
 of a 10'^ solution of sodium carbonate at the start, the rest of 
 the process remaining the same. 
 
 
 Time 
 
 Teinperature 
 
 °C. 
 
 ^ of Char 
 
 Tinctor- 
 ial no. 
 
 Acid Test 
 
 30 
 
 rain. 
 
 310 
 
 3.58fo 
 
 31' 
 
 10 min. 
 
 40 
 
 n 
 
 310 
 
 4. 63fo 
 
 35 
 
 13 " 
 
 50 
 
 n 
 
 310 
 
 6, 95“^ 
 
 45 
 
 15 " 
 
 60 
 
 tt 
 
 210 
 
 8,30fo 
 
 48 
 
 15 ” 
 
 The tinctorial strength was the only test benefited by this 
 method so it was discarded. Other test batches were cooked by 
 adding larger and smaller amounts of sodium carbonate, by adding 
 it at the end of the cooking instead of at the first and by adding 
 it in aliquot portions throughout the caraxasl izat ion prdcess, but 
 
V • 
 
 t 
 
 L 
 
 V 
 
 4 
 
 M 
 
 X 
 
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- 13 
 
 all of these experiments gave practically the same results. Erste 
 Wiener Export (loo. cit. ) stated that a satisfactory caramel could 
 be prepared by the addition of a very small amount of acid. Four 
 test batches were prepared by the addition of 5 cc. of dilute 
 hydrochloric acid (one p?-rt 6 N. hydrochloric acid to sixteen 
 parts of water) plus the 10 cc. of sodium carbonate solution 
 added at the beginning of the process. 
 
 
 Time 
 
 Temperature 
 
 ®C. 
 
 ^ of Char 
 
 Tinctor-r 
 ial no. 
 
 Acid 
 
 Test 
 
 30 
 
 min. 
 
 310 
 
 3.68f« 
 
 38 . 
 
 13 
 
 min. 
 
 40 
 
 n 
 
 310 
 
 3,98f. 
 
 39 
 
 13 
 
 It 
 
 50 
 
 It 
 
 310 
 
 5. 48*^ 
 
 38 
 
 13 
 
 n 
 
 60 
 
 I! 
 
 310 
 
 5.65fo 
 
 43 
 
 15 
 
 ft 
 
 The use of hydrochloric acid seemed to cut down the percent- 
 age of char but the tinctorial strength and the acid test remained 
 about the same. Sulfuric, phosphoric, and nitric acids were tried 
 with no improvement in the resulting caramel. It was very evident 
 that these reagents were out of the question for the preparation 
 of an acid fast color. 
 
 During the cooking of the test batches the caramel just at 
 
 the cracking point rose rapidly up to the neck of the flask and 
 frothed considerably. It seemed that if a method could be devised 
 to keep the caramel from frothing during the cararnelization process 
 the time of cooking would be greatly reduced. It was impossible 
 to use a stirring device that would scrape the sides of the flask. 
 

- 13 - 
 
 If the addition of a volatile chemical would keep the sugar in 
 constant motion and yet not affect the composition of the caramel, 
 the method of cooking would be greatly improved. Ammonium Chloride 
 was first tried. A series of batches were burned with the addition 
 of 5 cc. of a 10*^ solution of ammonium chloride at the beginning 
 of the batch. 
 
 
 Time 
 
 Temperature 
 
 °C. 
 
 ^0 of Char 
 
 Tinctor- 
 ial no! 
 
 Acid 
 
 Test 
 
 15 
 
 min. 
 
 200 
 
 8. 63fo 
 
 121 
 
 30 
 
 min. 
 
 16 
 
 n 
 
 200 
 
 8, 95 fo 
 
 126 
 
 30 
 
 
 17 
 
 ti 
 
 200 
 
 9,54fo 
 
 127 
 
 30 
 
 n 
 
 18 
 
 n 
 
 200 
 
 ll,65fo 
 
 135 
 
 30 
 
 1? 
 
 19 
 
 n 
 
 200 
 
 13. 48fo 
 
 133 
 
 30 
 
 ij 
 
 20 
 
 n 
 
 200 
 
 15.63fo 
 
 133 
 
 30 
 
 n 
 
 The results obtained by the use of the salt were surprising. 
 It took only one-third of the time previously required for the 
 caramel ization process, it did not froth, it gave a much higher 
 tinctorial number, and it was acid-fast. Apparently the batch 
 which was burned in 18 minutes gave the best results. Using this 
 time of heating and a temperature of 300°C. several batches were 
 prepared with different amounts of the salt. The left hand coluinn 
 represents the amount of 10^ solution of ammonium chloride used. 
 
- 14 - 
 
 Amount 
 
 Temperature 
 
 °c. 
 
 ^ of Char 
 
 Tinctor- 
 ial no. 
 
 Acid 
 
 Test 
 
 10 cc. 
 
 300 
 
 35.63fo 
 
 143 
 
 30 
 
 min. 
 
 9 " 
 
 300 
 
 34.03fo 
 
 140 
 
 30 
 
 n 
 
 8 " 
 
 300 
 
 19.35f» 
 
 141 
 
 30 
 
 n 
 
 y »i 
 
 300 
 
 16. 4Bfo 
 
 138 
 
 30 
 
 n 
 
 6 " 
 
 300 
 
 13.76fo 
 
 135 
 
 30 
 
 n 
 
 5 " 
 
 300 
 
 13.89fc 
 
 138 
 
 30 
 
 tt 
 
 4 
 
 ■ 300 
 
 9.05fo 
 
 131 
 
 35 
 
 n 
 
 3 " 
 
 300 
 
 3.35fo 
 
 96 
 
 15 
 
 n 
 
 It is obvious from these results obtained that 5 cc. of the 
 salt solution gave the best results. This amount of ammonium 
 chloride was used in combination with dilute solutions of hydro- 
 chloric, sulfuric, and phosphoric acids, but jjhe only difference 
 noted was a slight increase in the tinctorial number. Although 
 this method produces a satisfactory acid-fast caramel, the cost 
 of the aiamonium chloride is a little too high to be used in the 
 economical preparation of She compound. 
 
 Commercial an^aonium sulfate, which is much cheaper than the 
 chloride was next tried. A series of batches were cooked by 
 the addition of 5 cc. of a 10^ solution of ammonium sulfate at 
 the beginning of the run. The time of heating was varied but 
 the temperature was kept constant. 
 
- 15 
 
 Time 
 
 
 Temperature 
 
 °C. 
 
 
 ^ of Char 
 
 Tinctor- 
 ial no. 
 
 Acid Test 
 
 15 min. 
 
 
 300 
 
 
 6.33fo 
 
 135 
 
 35 min. 
 
 16 " 
 
 
 300 
 
 
 7,86f. 
 
 138 
 
 35 ” 
 
 17 " 
 
 
 300 
 
 
 
 131 
 
 30 ” 
 
 18 " 
 
 
 300 
 
 
 6.64f^ 
 
 143 
 
 30 " 
 
 18 " 
 
 
 SCO 
 
 
 10.83^; 
 
 144 
 
 30 ” 
 
 30 " 
 
 
 300 
 
 
 15. edfo 
 
 149 
 
 30 " 
 
 Again heating for a period of 18 minutes seemed to give the 
 
 best results, 
 
 . By varying 
 
 the 
 
 amounts of 
 
 the salt solu 
 
 tion and 
 
 heating at a 
 
 temperature of 300®C. for 18 
 
 minutes, the 
 
 quantity 
 
 of salt 
 
 necessary to give 
 
 the 
 
 best results was obtains 
 
 d. 
 
 Amount 
 
 
 Temperature 
 
 ®C. 
 
 
 ^ of Char 
 
 Tinctor- 
 ial no. 
 
 Acid Test 
 
 10 cc. 
 
 
 300 
 
 
 21, 61 fo 
 
 153 
 
 30 min. 
 
 9 " 
 
 
 300 
 
 
 33 . 45^ 
 
 151 
 
 30 ” 
 
 8 " 
 
 
 300 
 
 
 19.83fo 
 
 146 
 
 30 " 
 
 7 ” 
 
 
 300 
 
 
 21,07fo 
 
 143 
 
 30 ” 
 
 6 " 
 
 
 300 
 
 
 l5.93fo 
 
 138 
 
 30 " 
 
 5 ” 
 
 
 300 
 
 
 13.48f^ 
 
 140 
 
 30 " 
 
 4 " 
 
 
 300 
 
 
 6,52fo 
 
 136 
 
 30 ” 
 
 3 ” 
 
 
 300 
 
 
 4.8lfo 
 
 116 
 
 30 ” 
 
 In this 
 
 series of experiments 
 
 the 10 cc. 
 
 of salt solution seemed 
 
 to give 
 
 the 
 
 'oest caramel. 
 
 The amount of 
 
 salt was cut 
 
 dov\,m con- 
 
 siderably by 
 
 the addition 
 
 of 
 
 a small amount of acid. 
 
 The above^ 
 
- 16 
 
 experiment was repeated v;ith the addition of 3 cc. of dilute hydro- 
 chloric acid (page 10) at the beginning of every run. 
 
 Amount 
 
 Temperature 
 
 ®C. 
 
 fo of Char 
 
 Tinctorial 
 
 number 
 
 Acid 
 
 Test 
 
 10 cc. 
 
 300 
 
 16.05^ 
 
 168 
 
 30 : 
 
 min. 
 
 9 " 
 
 300 
 
 17.95f. 
 
 161 
 
 30 
 
 n 
 
 8 " 
 
 300 
 
 15.3lfo 
 
 158 
 
 30 
 
 n 
 
 7 " 
 
 300 
 
 10.65fo 
 
 145 
 
 30 
 
 n 
 
 6 " 
 
 300 
 
 13.77f. 
 
 .151 
 
 30 
 
 n 
 
 5 " 
 
 300 
 
 lO.OOffi 
 
 149 
 
 30 
 
 
 4 « 
 
 300 
 
 8.78fo 
 
 145 
 
 30 
 
 n 
 
 3 « 
 
 300 
 
 e.3Zfo 
 
 130 
 
 35 
 
 n 
 
 The presence of the acid reduces the amount of salt required 
 to about one-half, as seen clearly by the last two experiments, 
 the quality of the product being practically the same in both 
 cases. An attempt was made to substitute sulfuric and phosphoric 
 acid for the hydrochloric but a very poor product resulted from 
 the use of both of these acids. The preparation of an acid-fast 
 caramel can best be effected by caramelizing in the presence of 
 a small amount of ammonium sulfate and a weak solution of hydro- 
 chloric acid. 
 
 There is present in ordinary carai^iels a small amount of un- 
 changed sugar. The methods of purification used to remove this 
 sugar are enumerated by previous investigators, vho purified the 
 
- 17 
 
 the product were; precipitation by alcohol, fermentation, and 
 
 ( 10 ) 
 
 dialysis. The first two methods were considerably harder to use 
 than the last method and were not employed for the purification of 
 the caramel. 
 
 For experimental purposes caramel can be purified very readily 
 by dialysis through a collodion membrane,. The membrane ms 
 prepared by rotating the collodion solution in a 350 cc. Erlenmeyer 
 flask, pouring off the excess collodion, allov/ing it to dry over 
 night, and drawing out the bag with the assistance of a fine stream 
 of water. The bags prepared in this manner were water tight and 
 were sufficiently strong. 
 
 About 300 oc. of the caramel solution was poured in one of the 
 bags with a small capillary tubs fastened in the constricted end 
 of the bag and then supported in a large beaker containing distilled 
 water, with the v/ater and the solution in the bag at the same level. 
 The caramel solutions were allowed to dialyze for 48 hours, the 
 water being changed several times during the process. The caramel 
 solutions and the water solutions outside the bag were then tested 
 for the absence or presence of sugar, formaldehyde, and acetic 
 acid. 
 
 In the dialysis of caramels prepared without the use of chem- 
 icals the unchanged sugar, formaldehyde, and acetic acid passed 
 through the bag very rapidly as sho^vn by qualitative tests applied 
 at different intervals to the water solution. The resulting car- 
 amel contained none of the above mentioned substances, When boil- 
 6d_ vith hydrochloric acid thg solution remained clear for over 30 
 

- 18 
 
 minutes showing that the purified product was acid-fast. 
 
 The caramels prepared by the use of the ammonium salts were 
 next dialyzed for a period of 48 hours. The water solution at 
 the end of the first 13 hours gave absolutely no tests for sugar, 
 formaldehyde, acetic acid, and ammonium salts. At the end of the 
 46 hours the water solution was slightly acid to litmus and gave 
 evidence of a trace of the ariimonium salts. The caramel solution 
 was acid-fast, both before and after dialysis. It is evident from- 
 these experiments that the acid-fastness of a caramel depends 
 upon the absence of the unchanged sugar, as the action of the 
 dilute hydrochloric acid on the sugar causes hydrolysis with the 
 formation of a murky solution. 
 
~ 19 
 
 IV 
 
 AH IHVESTIGATIOH OF THE PURIFIED CARAMELS. 
 
 One of the most interesting studies on the subject of 
 caramels since the earliest investigations has been the determin- 
 ation of a suitable empirical formula for the compound. Results 
 have differed so v/idely on this value that it seems probable that 
 there is a different compound formed with each different method of 
 preparation of the caramel. To reach a satisfactory proof of this 
 statement the molecular weights of oaramesl prepared by two differ- 
 ent processes were determined. 
 
 The freezing point method was used in this investigation and 
 although it was extremely hard to get check results, seven deter- 
 minations wore run on each caramel to obtain a satisfactory aver- 
 age. The average of the res’ults obtained check fairly close with 
 
 ( 11 ) 
 
 the value given by Beal and Zoller for the molecular weight of 
 a glucose caramel. The first series of determinations were made 
 on the purified product obtained from the ordinary distillation 
 of commercial glucose. 
 
 Glucose caramel — -503-509-513-514—506-509-511 
 
 Average 509,8 
 
 This value of 509.8 checks reasonably close v/ith the value of 
 516, as obtained by Zoller, and seems to indicate the empirical 
 formula of this caramel would be CgoHaoOis* 
 
- 30- 
 
 Howevsr, in the determination of the molecular weights of 
 the caramels prepared by the use of the aniinonium salts an entirely 
 different value ?;as obtained, A series of molecular weight de- 
 terminations v/ere made eon the ammoniuirx sulfate caramel and the 
 average value wasx. considerably less than that obtained above. 
 
 Glucose Caramel 458 -470-466r5- 493 -489-495 -488 
 
 Average -484. 8 
 
 This average would call for empirical formula of CisHsoOib which 
 appears entirely possible. Zoller also points out that the glu- 
 cose caramel might possess a polymeric hexose structure as 
 (C 6 Hi 206 ) 3 * The action of the ammonium sulfate on the oarameliza- 
 tion process accelerates the dehydration of the molecule and 
 if this formula was assumed correct the action of the salt might 
 be illustrated by the following equation. 
 
 (C ©Hi 303)3 ^ ( C 6 ^'^io^s ) 3 + 3 KsO 
 
 The formula (CeH 1005)3 would call for a molecular weight of 486, 
 which approximates very closely the value obtained experimentally. 
 Hydrolysis of the Benzoyl Derivative. The benzoyl derivative 
 was prepared by shaking the acidpfast caramel with a slight ex- 
 cess of benzoyl chloride in the presence of sodium hydroxide. 
 
 The derivative thus prepared had a light brown color and appeared 
 to be a mixture. It was not entirely soluble in glacial acetic 
 acid, much less in other comon solvents, so that a molecular weight 
 determination could not be made by the freezing point method. 
 
- 31 
 
 In order to obtain some knowledge of the number of benzoyl 
 groups which had been substituted for the hydrogen of the hydroxyl 
 groups, the derivative was hydrolyzed and the percentage of benzoic 
 acid determined. 3 grams of the purified derivative were v/eighed 
 accurately into a 500 cc. flask. Exactly 50 cc. (measured from a 
 pipette) of a standard 10*)?’ solution of sodium hydroxide were then 
 added and the mixture refluxed for thirty minutes. The clear 
 solution was then poured into a liter volumetric flask, made up 
 to the mark, and 50 cc. removed for titration. The excess alkali 
 7/as titrated with 0.5 N. hydrochloric acid, using a mixture of 
 methyl red and methylene blue as an indicator. The amount of 
 benzoic acid was then very readily calculated. 
 
 The average amount of benzoic acid calculated from a series 
 of titrations was 4.98)^. This axiiount is very low and it shows 
 clearly that the number of benzoyl groups attached in the derivative 
 are comparatively few. 
 
Tt 
 
 
 
 *■ • ’ ■; ' . ■ ' ■ ^ : 
 
 •-■Hr'* -4 ' 
 
 " ‘I’ ^.. 
 
 
 , ,♦.*• .y 
 
 4*. ■ i 
 
 I.' ^ r 
 
 
 
 f 
 
 
 
 
 V 
 
 
 i 
 
 7 
 
 / ;>■ 
 
 *v 
 
 
 
 - ■ 
 
 -H 
 
 < ; 7 
 
 
 I >• • \ ■ .f 
 
 
 * / t j » ' 
 
 r *y» ^ 
 
 
 
 
 
 \ 
 
 i j< : 
 
 
 1 
 
 
 I 
 
 ^ V. 
 
 
 / 
 
 Tv, 
 
 
 ki 
 
 / 
 
 A 
 
 ‘W 
 
 I -It 
 
 r 
 
 '• 
 
 fr- “< - • -V ■vC*..'- •*»*>*■ “ ■ 
 
 T- r •*■ 
 
- 33 
 
 V 
 
 CONCLUSIONS 
 
 (l) A satisfactory caramel can be prepared by the 
 caramelization of a commercial glucose in the presence of 
 a small amount of armnonium sulfate and hydrochloric acid, 
 
 (3) The amionium sulfate and hydrochloric acid act 
 purely as catalysts and probably accelerate the dehydration 
 of the molecule. 
 
 (3) Acid-fast caramels contain no unchanged sugar as 
 illustrated by the dialysis of the caramels through a collod- 
 ion rflembrane. 
 
 (4) Caramels prepared by different methods have different 
 values for molecular weights and consequently must have vary- 
 ing molecular structures. 
 
 (5) The number of hydroxyl groups in the caramel molecule 
 is dependent upon the completeness of the dehydration of the 
 molecule, the more complete the dehydration, the fewer the 
 hydroxyl groups, as sho'im by the percentage of benzoic acid 
 
 in the benzoyl derivatives. 
 
23 
 
 VI 
 
 BIBLIOGRAPHY 
 
 (l^ Ann. de Chemique et Physique, 2nd ser. 67-172-1838. 
 
 (2) Annalsn der Cherai. Vol. 85-86-89-1853. 
 
 (3) .Ann. de Chemique et Physique, Vol. 52-352-1858 
 
 (4) Bui. de la Societe Chemique de Paris, 90-681-1906. 
 
 (5) J. Chem. Society, 111-589-608-1917. 
 
 (6) Z. Suikerind Bijblad, No. 40-497-524-1910. 
 
 (7) Deut. Zuckerind, 35-617-618. 
 
 (8) J. Inst. Brewing, Vol. 8-673-686-1913. 
 
 '.(9) . Malzfabrik House and Sobotka, Dan. 24-843-1919. 
 
 (10) . Beal and Zoller, Jour. Amer. Pharm. Assoc., April, 1914, 
 
 490. 
 
 (11) ' Beal and Zoller, Private Communication.