INDUSTRIAL AND ENGINEERING CHEMISTRY
744
water oven drying by 1 to 3 per cent, because of the different forms in which water is present in flour-namely, (1) free moisture, (2) that held more tenaciously (physically), and (3) that chemically united with the carbohydrates and proteins as water of hydration. With a wide range of temperature and pressure conditions in flour moisture determinations, these separate forms of water are removed a t different rates and in varying amounts. I n Pgrt I1 a more extended discussion of these various forms of water will be given-principally the water held by the proteins as water of hydration and that held by the starch and other carbohydrates which are formed from the starch as its moisture is gradually removed. The lack of accurate methods for the determination of moisture in flour and cereal products is a handicap in many ways. It augments the error carried by that heterogeneous class of compounds called nitrogen-free extract, as well as affecting the dry matter basis of every analytical determination. I n flour mill and other control work there is need of a simple, reasonably satisfactory method standardized against water oven, or some recognized method, one having an es-
Vol. 16, No. 7
tablished factor of difference with both water oven and extreme vacuum oven drying. While any such method may lack analytical perfection, its ordinary limits of error will be known and can be taken into consideration in dealing with flour moisture problems. A well-equipped chemical laboratory, including a vacuum oven ouhfit and employment of a skilled chemist, while essential for flour investigations, involves a prohibitive expense for a medium-sized or small flour mill, and such mills produce over half the flour consumed in this country, hence the necessity of conventional control methods. But a conventional method for determining moisture in flour for control work does not entirely solve the problem, for a method that gives closely agreeing results does not necessarily give accurate results. I n flour investigations a chemist cannot always follow didactic or empirical methods. It is quite important that the analyst give the essentials of the moisture method he uses so that comparisons of results by different methods can be intelligently made. Particularly is this necessary in making comparisons of moisture tests by the water oven, the extreme vacuum oven, and other methods of drying.
The Catalyzed Oxidation of Galactose' By E. 0.Whittier RESEARCH LABORATORIES, DAIRYDIVISION,U. S. DEPARTMENT O F AGRICULTURE, WASHINGTON, D. C.
T
The oxidation of galactose by nitric acid is accelerated by the presb e o x i d i z e d directly to H E purpose of this work was to ascertain oxalic and carbonic acids ence of oanadium pentoxide. No other substance tested showed any catalytic e&ct on this reaction. without intermediate forthe nature and magThe optimum concentration of nitric acid for mucic acid producmation of tartaric and sacnitude of the effects of cataacids. S c h m i d t lysts On the oxidation of tion from galactose at 85" C . under laboratory conditions is about 35 tried the effect of fifty difgalactose to mucic acid by pey cent by weight. Concentrations higher than 35 per cent have means of nitric acid. This the e&ct of increasing the production of oxalic and carbonic acids ferent elements-in most cases in the form of saltsiS Of interest in Connection at the expense of mucic acid. with the possibility of comThe presence of vanadium pentoxide in nitric acid of concentraon the reaction between tions of 35 per cent or greater increases the production of oxalic and Sucrose and nitric acid. He mercial production of mucic carbonic acids at the expense of mucic acid over and abooe the amount detected catalytic effects acid from lactose O r @lacdue to the acid concentration alone. only in the experiments tam2 The results indicate that oanadium pentoxide should not be emwhere vanadium, molybdeThe principal by-product played as a catalyst in the manufacture of mucic acidfrom galactose num, manganese, tin, and of this reaction is oxalic acid, though traces of the tartaric and related compounds. iron were used. He tried the effects of the same fifty acids are probably formed, substances on the reaction since they have been isolated between oxalic acid and nitric acid, and obtained evidence from oxidations of lactose by nitric acid.3 Kent,4 and Kent and Tollens6claim that the largest yields of of catalysis only in the experiments employing compounds mucic acid from lactose and from galactose can be obtained of vanadium and manganese. by warming with 12 parts of nitric acid of specific gravity 1.15. EXPERIMENTAL Published work on the catalysis of the oxidations of carbohydrates by nitric acid has been confined to starch and suPreliminary experiments were carried out with nine deerose. Ode116 employs chiefly vanadium and molybdenum ments which previous workers had shown to exert catalytic compounds in his process for producing tartaric acids from effects on oxidizing Processes. Cerium, iron, mercury, starch. Lindenbaum,7 and Naumann, Moeser, and Linden- manganese, and thorium were used as nitrates; molybdenum, baum* state that the presence of vanadium causes sucrose to vanadium, and tungsten as oxides; and Platinum as chlorideOne ten-thousandth gram atom was used except where 1 Received February 25,1924. Presented before the Division of Organic otherwise noted. Various concentrations of nitric acid were Chemistry at the 67th Meeting of the American Chemical Society, Washused, sufficient being weighed out to give 17.5 grams of actual ington, D. C., April 21 to 26, 1924 2 Acree, Brltish Patent 160,777 (1921), Schorger, Canadian Patent HXO, for each experiment. The catalyst was added, the 213,175 (1921). acid solution brought to 86" C., 1 gram of the substance to be 8 Liebig, Ann., 113, 1 (1860); Hornemann, J. Brakt. Chem., [ll 89, oxidized introduced, and the mixture maintained a t 86" C. 283 (1863). for an hour. The solution was then transferred to a beaker 4 Dissertation, Gottingen, 1884. 8 Ann.. 2%7, 222 (1885). containing sodium hvdroxide solution, and a few drops of 6 U. S. Patent 1,425,604 (1922). phenolphchalein wer;! added. Sufficient sodium hydroxide 7
8
Dissertation. Giessen 1906. J. prakt. Chem., [2] 76, 146 (1907).
9
Dissertation, Giessen, 1913.
INDb-STRIAL AND ENGIATEERING CHEiVIISTRY
July, 1924
solution was added to make the solution alkaline; it was then acidified with 10 per cent acetic acid. Mucic and oxalic acids in mixture were determined by the author's method,1° oxalic acid when alone by the usual volumetric method. Galactose, mu.cic acid, and oxalic acid were the substances chosen for oxidation.
745
nearly the whole range of acid concentrations the reactions were proceeding in a practically identical manner throughout the time of reaction and were incomplete a t the end of the reaction period. Consequently, none of the values given a p p r o a h the yields of mucic acid obtainable when the reaction is allowed to continue for a longer time. The results are recorded in Table I1 and plotted in Fig. 1. Each value given is the average of several oxidation:. TABLE 11-OXIDATION OF G A L A C T ORSY~NITRICACID Temperature, 85O C. Time, 1 hour 1 gram galactose 17.5 grams actual HNOi Catalyst, 0,0091 gram VzO6 "OB Concn. ---OXALIC ACID------MUCIC ACID-Per cent Not Catalyzed Catalyzed Not Catalyzed Catalyzed by Weight Grams Grams Grams Grams 25 0.0000 0.0000 0.0003 0.0000 30 0.0103 0.0190 0.2985 0.3274 35 0.0525 0.0817 0.4765 0.3873 40 0.1166 0.1550 0.4812 0.2840 45 0.1896 0.2596 0.3792 0.1996 50 0.1696 0.3067 0.3843 0.0290 55 0.2197 0.4236 0.3582 0,0180 60 0.2510 0.4256 0.3176 0.0000 65 0.2151 0.4693 0,2728 0.0000 70 0.2391 0.4542 0.2591 0.0000
DISCUSSIOX
Conc. o f Nitric Acid
- % by weigbt
FIQ. 1
Vanadium pentoxide was the only substance that showed any effect on the oxidation of galactose by nitric acid. Its most pronounced effects were in the higher nitric acid concentrations, where it caused the amount of mucic acid formed to be greatly reduced and the amounts of oxalic and carbonic acids to be increased. Nitric acid does not attack mucic acid perceptibly under the conditions of these experiments, except when vanadium is present. I n the presence of vanadium, 70 per cent nitric acid oxidized approximately 30 per cent of the mucic acid present, 60 per cent nitric acid oxidized approximately 22 per cent, 50 per cent nitric acid approximately 12 per cent, and 40 per cent nitric acid only a trace. Oxalic and carbonic acids were produced in approximately equal quantities. The oxidation of oxalic acid was catalyzed by vanadium pentoxide, cerium nitrate, and manganese nitrate. The relative activity of the catalysts, and the influence of concentration of oxidizing agent and of catalyst are shown in Table I. This table is also of interest in connection with the yields of oxalic acid from the oxidation of galactose, as shown in Table 11. TABLET-INFLUENCE OP CATALYSTS, CONCENTRATION OR CATALYST, AND COXCBNTRATION OF OXIDIZING AGENTON NITRIC ACID OXIDATION OF OXALICACID Temperature, 85O C. Time, 1 hour 1 gram oxalic acid 17.5 crams actual "01 .-Concentration 7of -s0" Catalyst Gram Atoms 40% 30% 60% 50% 70% 0.0 0.0 5.5 0.0 7.7 None 6.4 2.1 9.8 7.7 0,0001 cerium 18.0 11.3 7.4 21.3 14.7 0.0001 manganese 30.7 12.7 9.5 52.7 36.0 90.6 0.0001 vanadium 28.0 18.3 72.0 54.3 0.0002 vanadium 95.6 93.7 69.1 37.8 23.0 99.9 0.0004 vanadium
An extended series of oxidations of galactose was then carried out according to the procedure previously described. The concentrations of nitric acid ranged from 25 per cent by weight to 70 per cent by weight. The catalyst used was 0.0091 gram vanadium pentoxide-e. g., 0.0001 gram atom vanadium. This set of conditions was selected because over 10
Whittier, J . A m . Chem. Soc., 45, 1391 (1923).
The changes in curvature of the plotted values a t 60 per cent nitric acid concentration are due partially to the slowing down before the end of the hour of the reactions at these high concentrations, and partially-in the case of the oxalic acid curves-to oxidation of oxalic acid. The principal reactions taking place at low nitric acid concentrations are the oxidation of galactose to mucic acid and oxidation of galactose to oxalic acid. At higher concentrations of the acid, galactose is evidently oxidized directIy to carbon dioxide and water, even in the absence of vanadium. The optimum concentration of nitric acid for maximum mucic acid production a t 85" C. is in the vicinity of 35 per cent. At this concentration oxalic acid is formed, but in comparatively small amounts. At lower concentrations the rate of production of both acids falls off rapidly. At higher concentrations the amount of mucic acid formed in a given time is less, and the amount of oxalic acid is greater, than a t 35 per cent. Vanadium apparently catalyzes positively, but to a slight degree, the oxidation of galactose to mucic acid by 30 per cent nitric acid. It appears to have the opposite effect a t higher concentrations but this apparent effect is probably due to the preponderance of the reactions producing oxalic and carbonic acids, which are both accelerated by vanadium. The catalytic effect of vanadium on the oxidation of galactose to oxalic acid is clearly evident, even a t the higher nitric acid concentrations where the oxidation of the oxalic acid itself is being catalyzed. The large number of factors involved in these reactions makes a discussion from the standpoint of the law of mass action impracticable.
Industrial Standards in Advertising M a t t e r As a definition of policy concerning the use of references inadvertising matter to standards approved by the American Engineering Standards Committee, the following resolution has been adopted: Resolved, t h a t in the opinion of t h e American Engineering Standards Committee t h e use, in t h e advertising of products which comply with specifications and other standards approved by t h e Committee, of proper references t o such standards, is advantageous and makes for industrial economy; accordingly, the Committee desires t o encourage the use of such references in trade catalogs and other advertising media, b u t the Committee will in no case pass upon t h e merit of products, or upon their compliance with specifications or other standards, which questions it will leave t o the commercial and legal agencies equipped for such work.
Such references are frequently made by foreign manufacturers in advertising products made in accordance with the standards of their national standardizing bodies, particularly in Great Britain and Germany. Both the British and Canadian associations have adopted official trade marks for use on goods manufactured in accordance with their specifications.
