December, 1925 PIGM5NTS
None Burnt American umber
INDUSTRIAL A N D ENGINEERING CHEMISTRY Concentration of lead in centrifuged liquid Per cent 0.094 Faint trace
The centrifuged vehicle from the paint made with umber gave a distinct test for manganese. It is obvious that the failure of umber to retard the initial rate of oxidation of the
1257
oil is due to the formation of a small amount of manganese drier by the interaction of the oil and the pigment. METALLIC BROWN(Figure 4)-Paints made from metallic brown as a pigment behave very much like paints made from domestic ocher, although both the decrease in the initial rate of oxidation and the increase in the final rate of oxidation are somewhat less pronounced.
Preparation of I- Arabinose from Mesquite Gum'.* By Ernest Anderson and Lila Sands UNIVERSITY OB ARIZONA, TUCSON, ARIZ. t h a t it can be powdered in a mortar. Arabinose is readily prepared by the hydrolysis of H E preparation of ZThis gum is collected by the Indians 3 hours at 80" C. in six times its mesquite gum for arabinose from variand Mexicans. It is carried by most weight of 4 per cent sulfuric acid. After removal of the of the d r u g stores of Tucson and ous plant products has acid as barium sulfate the neutral solution is conwith a few weeks' notice could be frequently been described in supplied in large amounts by the centrated, the salts precipitated by alcohol, and the t h e l i t e r a t u r e U a Browne4 Martin Drug Co., of Tucson, at 30 alcohol solution of the sugars concentrated and allowed gives the general method c e n t s o r l e s s p e r p o u n d . Unto crystallize. The yield of crystalline sugar varies doubtedly other chemical supply followed in the preparation from 27 to 36 per cent of the gum used and the melting houses of the Southwest, such as t h e of the sugar. Lippmann,6 Mine & Smelter Supply Co., of EL point varies from 140" to 155" C. This product can be Abderhalden6 and Beilstein,' Paso, could secure large amounts recrystallized from water, mixtures of water and algive reviews of the literature of the gum. Mesquite gum is fully cohol, and from glacial acetic acid. Mesquite gum can dealing with the preparation, described in an article by Anderson, be purchased in large amounts in the Southwest. Sands. and Sturais. A m . J . Pharmtogether with numerous refacy, ST, 589 (1925). e r e n c e s . Hudson,$ states Dissolve 500 grams of mesquite gum in 3 liters of water that beet pulp is a better source of arabinose than cherry gum, which is usually recommended by textbooks. Hard- contained in a 5-liter flask. (If the mixture of mesquite gum ings prepares arabinose by hydrolyzing beet pulp for 1.5 and water is let stand for 10 hours and then shaken it will hours in a boiling 1 per cent solution of sulfuric acid and ob- form a clear solution. The same result can be attained by tains from 4 to 5 per cent of the beet pulp in the form of heating the mixture in the boiling water bath for an hour arabinose. with frequent stirring. The acid should not be added until The present investigation was undertaken in connection the gum is dissolved.) To this solution add a cool solution with the study of plant gums. The crude material, mesquite of 125 grams of concentrated sulfuric acid in 70 cc. of water, gum, has been found to give good yields of the I-arabinose and heat to 80" C. for 3 hours in a large water bath. Prewhen prepared by the following method. cipitate the sulfuric acid by adding to the hot solution, a hot concentrated solution of 410 grams crystalline barium N o l e M e s q u i t e gum is found on the mesquite tree, Prosopis juliffora, hydroxide. (The barium hydroxide should not contain more a n d other species of mesquite, through a great part of Texas, New Mexico, than traces of carbonate or the solution will foam.) AdArizona, and northern Mexico. The gum exudes from the stem and brancher just the solution to neutrality by adding small amounts of in irregular, roundish, or vermiform pieces of various sizes, usually small, barium hydroxide solution or sulfuric acid solution as reweighing 5 grams or less, but sometimes weighing a s much a s 25 grams. When the gum first appears i t is soft and sticky. At this stage it often runs quired. Let the barium sulfate settle, siphon the clear soludown the branch. It gradually dries out and becomes hard and so brittle tion, filter the barium sulfate on a Buchner funnel, and wash it with hot water. Combine the solutions and concentrate 1 Received June 24, 1925. Presented before the joint meeting of the in an evaporating dish on the boiling water bath, to a volume Divisions of Organic Chemistry and Chemistry of Medicinal Products a t of approximately 650 cc. When the gum is hydrolyzed at the 70th Meeting of the American Chemical Society, Los Angeles, Calif., 80" C. the water cannot be distilled off in vacuo because of August 3 to 8, 1925. foaming but must be evaporated in an open dish. Transfer 2 This is the first of a series of papers dealing with the chemistry of the plant gums in general and especially with those t h a t occur in the souththe solution to a 3-liter flask. The total volume should be western part of the United States. 700 cc. To this solution add with shaking 1.5 liters of 95 8 Scheibler, Ber., 1, 58 (1869); 6, 612 (1873); Allen and Tollens, A n n , per cent ethyl alcohol. Let stand until the solution is no 260, 289 (1890) ; Ullick, 2. Zuckerind. u. Landw., 23, 274 (1894); Marquardt longer turbid. Decant the sugar solution from the gummy and Schulz, 2. Ver. deul. Zuckerind., 51, 864 (1901); Bauer, Ibid., 36, 751 (1886); J . prakf. Chem., 30, 367 (1884); Kiliani, Ber., 19, 3029 (1886); barium salts and extract the latter four times under the Ruff and Meusser, Ibid., 34, 1364 (1901); Subascbow, Z Ver. derrl. Zuckerreflux, each time with 500 cc. of boiling methanol (prepared ind., 46, 270 (1896); Tollens and Browne, Ber., 36, 1464 (1902); Tollens, by distilling wood alcohol over quicklime). After the Z . angew. Chem., 20, 477 (1902); Steiger and Schulze, Ber., 23, 3110 (1890); third extraction transfer the salt to an evaporating dish and Schulze, 2. Dhrsiol. Chem., 16, 386 (1892); Wroblewski, Ber., 30, 2289 (1897); 31, 1128 (1898); Yoshimura, Chem. Zenfr., 1896, 46; Winterstein grind to a powder. Concentrate the ethyl alcohol solution and Blau, 2. physiol. Chem., 76, 410 (1911); Power and Salway, J . Chem. of the sugars in vacuo on the boiling water bath to a thin sirup. SOC.(London), 103, 191 (1913); Kiliani and Koehler, Ber., 87, 1210 (1904); (If all the water is removed by heating the gum in vacm Houers and Tollens, Ibid., 36, 3306 (1903). Handbook of Sugar Analysis, 1912, p. 548. for some time the sugar will not crystallize. Seeding with 6. "Chemie der Zuckerarten," Vol. I , 3rd ed., 1904, p. 55. crystals of arabinose hastens crystallization.) Let this cool. 6 Biochemische Handlexikon, 1911, Vol. KI, pp. 21,279; Vol. VIII, p. 112. After crystallization has begun add a small volume of ethyl ' Handbuch der Organischen Cbemie, Vol. I, 4th ed., 1918, p. 860. alcohol, being careful not to precipitate an appreciable amount a THIS JOURNAL, 10, 177 (1918). ' C. A . , 17, 1164 (1923). of gummy material. Set the solution in the refrigerator,to
T
INDUSTRIAL AND ENGINEERING CHEMISTRY
I258
complete crystallization, filter off the crystals, wash with 95 per cent alcohol, and dry. Combine the filtrate with the methanol extract of the barium salts, shake, let settle, pour away from any gum, concentrate the solution in vacuo, and secure a second crop of crystals as directed above. The filtrate from the first two crops of crystals contains gummy material, which frequently interferes with the crystallization of the sugar. To avoid this difficulty, remove all the solvent by distillation in vacuo on the boiling water bath. Dissolve the residue in a small volume of hot methanol. Precipitate the gum along with a small amount of sugar by adding a limited amount of 95 per cent ethyl alcohol. (Avoid excess alcohol since it will precipitate most of the sugar.) Decant the sugar solution from the small amount of gum, remove the solvent from the sugar by distillation in vacuo on the boiling water bath, dissolve the.sugar in a small volume of hot methanol, cool, seed with pure arabinose, and set in the refrigerator to crystallize. Filter off the crystals and repeat the process twice. The yield of crystalline arabinose varies from 25 to 36 per cent of the mesquite gum used-i. e., from 125 to 180 gramsand the melting point varies from 140"to 155"C. I n general, the first two crops of crystals are easily obtained and represent from 22 to 25 per cent of the gum used. Purification
Dissolve the crystals obtained above in eight times their weight of hot water and decolorize with charcoal by heating the solution to gentle boiling for half a n hour. Filter the hot solution on the pump and concentrate the filtrate in vacuo on the boiling water bath to a small volume. Transfer the hot solution to a beaker and rinse the flask with enough hot water to make the total volume in cubic centimeters the same as the original weight of the sugar in grams. To prevent the formation of a hard cake in the beaker, stir the mass while it is cooling. When the material is cold, add 20 cc. of 95 per cent ethyl alcohol for every 100 grams of sugar used, mix, and filter off the crystals. Transfer the crystals back to the beaker, triturate with 30 cc. of ethyl alcohol for every 100 grams of sugar used, filter, and dry the crystals. When the melting point of the original sugar is above 140' C. the yield of the first crop of purified crystals will be 70 per cent of the sugar used. The product should be perfectly white and melt at 148" to 151' C. Concentrate the filtrate from the first crop and secure a second crop of less pure material. By crystallizing the purified material twice from a mixture of its weight of water and four times its weight of 95 per cent ethyl alcohol a product is obtained melting a t 156" to 160" C. Crude crystalline arabinose cannot readily be purified by crystallization from dilute alcohol, but should first be recrystallized from water. It can be readily crystallized from glacial acetic acid.g Discussion
The results of pentosan,lO and mucic acid" determinations on mesquite gum correspond to 60 per cent pentoses and 11 18
*I
Pervier and Goertner, THIS JOURNAL, 15, 1167 (1923). Assoc. 0 5 c i a l Agr. Chem. Methods, 1919, p. 97.
-
Table 11-Hydrolysis Temp. . Period of of hydrolysis hydrolysis Fxpt. O C. Hours 1 80 2 2 80 2 2 8 80
4 6 6
7 8 9
SO
97 97 97 97 90
Alcohol used to ppt. Ba salt Liters 2 (95%) 1(95%) 0.7(95%)
-1st
Grams 65 81 54.5
Vol. 17, No. 12
per cent galactose. Hydrolysis of the gum in six times its weight of 4 per cent sulfuric acid yields a solution containing amounts of sugar that vary with the temperature and period of hydrolysis. Table I shows that in 4 per cent sulfuric acid the amount of reducing sugar present increases with the period of hydrolysis up to 20 hours.I2 of Hydrolysis of Mesquite G u m b y 4 Per c e n t Sulfuric Acid under VaryIng Conditions Temperature, OC.. SO 97 97 97 Period of heating, hours.. .................... 3 3 7 20 Per cent of gum obtained as sugar in solution 50 57 63 66 a The sugar was determined by Fehling's solution and calculated as pentoses (Assoc. Official Agr. Chem. Methods, 1919, p. 94.) Table I-Degree
..........................
Although the degree of hydrolysis of mesquite gum is increased within certain limits by an increase in the period of hydrolysis, repeated hydrolyses varying from 1 to 20 hours in the boiling water bath have shown that the longer the mixture is heated after 3 hours the lower is the yield of crystalline arabinose and the less pure the product. Furthermore, the crystalline arabinose obtained by hydrolysis of the gum at 80" C. was found to contain no galactose, while that obtained by hydrolysis in the boiling water bath generally gave the mucic acid test, thus indicating the presence of galactose. Apparently, hydrolysis at 80" C. leaves most of the galactose combined with the gum, which is later precipitated as a barium salt. At the same time the lower temperature decreases the decomposition of the free sugar and thus facilitates the crystallization of the arabinose. The yield of crystalline arabinose is grciatly influenced by the amount of 95 per cent alcohol added to precipitate the salts. If too little alcohol is added, considerable gummy material remains with the sugar and hinders its crystallization. If too much alcohol is added some of the arabinose is precipitated along with the salts. The amount of alcohol required is determined by the amount of water left in the sirup after concentration. Some of the highest yields of arabinose were obtained by the use of only 1 liter of alcohol to precipitate the salts. When the gum is hydrolyzed a t 80" C. and 2 liters of alcohol are used a portion of the arabinose is precipitated. When the gum is hydrolyzed in the boiling water bath for 3 hours it is necessary to use 2 liters of alcohol to precipitate the salts, in spite of the possible loss of sugar. Fermentation by yeast after hydrolysis of the gum was tried several times, but did not increase the yield of crystalline arabinose. The arabinose was identified by its rotation, flO5, its melting point, by the fact that seeding the gums with crystals of pure arabinose caused the formation of crystals, and by conversion to the p-bromophenylhydrazone, m. p. 155" C.I3 Table I1 summarizes the results of nine experiments on the hydrolysis of mesquite gum. 12 Abderhalden, Biochemisches Handlexikon, Vol. 11, p. 21, states that the per cent sugar increases to a maximum and then decreases on long hydrolysis of certain gums by a strong acid. 1: Fischer, Ber., 27, 2490 (1894).
of 500 Grams Mesquite Gum b y 3 Liters of 4 Per c e n t Sulfuric Acid
YIELD OF CRYSTALS cropM. p.
C. 153 150 143 152
O
125 150
-2nd
cro
Grams
90 56 38.5 93 110 29
143 140 147 156 145 147 110 Gummy 150
-3rd
Grams 10 31 62.5 6 49
..
27 19 8
cropM. p. C.
140 140 141 ... 145 95 G&& 110
- 4 t h cropM. p. Grams O C. 15 130 140 15 145 13 149 13
... ...
... 4.5
...
... ... ... 126 ...
T
-TotalGrams 180 188 168.5 133 156 150 134 192.5 142
yo 36
36.6
33.7 27 31 30 27 38.6 28
Ba salts Grams 260 280 260 280 194
220
idd
...
