INDUSTRIAL AND ENGINEERING CHEMISTRY
422
three wares fall in the order of their relative weights. However, there is a wide range in the indiedual values in each group, probably because of variations in thickness and in the amount of surface checking and scratching incident to handling.
Vol. 13, No. 6
(4) Souder, Wilmer, and Hidnert. Peter, Bur. Standards. Sci. Papen
21, l(1926); S524. (5) Walker, P.H. and Smither, F. W., Tech. Paper B w . Standard8 TI07 (1918): J. IND. ENG.CHEM.,9,1090 (1917). (6) Wiohers. Edward, Finn. A. N., and Clabaugh. W. S., J . Research Natl. Bur. S t a d m d s , 26,537 (1941);RP1394.
TABLE 111. RESISTANCE TO THERMAL SHOCK Tempmatwe 0
c.
ATer%e, breabnr temperature
Number of Breaks GLaahske Kirnble Pyre. Group A Group B Group A Group B Group A Group B
253
230
240
210
294
287
The relatively large number of this group whioh broke et 115. mugsested that B Lower starti% temperature ahould have been used: Aooordingly sna
other aet of 1s %aka was tested under the !=me oondrtions except with II ataitlns temperature of 1 2 5 O C. None of this moup broke a t 125" or 150' snd the 8ver8gn breaking temperature WBS 23s' C.
Resistance to Thermal Shock Resistance to thermal shook W&E determined (by Donald Hubhard) hy slowly heating a flask, containing 1CfJ ml. of a high-flash mineral oil, on a hot plate to a selected temperature and then quickly immersing it to the neck in ice water. If the fisk did &t break it was heated to a higher temperatuture and again suddenly chilled. This was repeated with increments of 25* C. until the flask cracked. Early in the tests it was noted that the average breaking temperature was higher for flasks which had been carefully removed from their wrappings and tested directly than for flasks whioh had been handled somewhat, in about the way glassware iscommonlyhandled from thetimeit leaves thestoreroom shelf until it has been cleaned and otherwise made ready for its first service in the laboratory. This handling involved relatively gentle contact of the flaslrs with one another and with the laboratory bench, which undoubtedly causes minute surface injuries, usually too slight to be visible. Accordingly, tests were made of two groups of eighteen flasks of each brand (except Vycor). One group was tested directly as removed from the shipping containers and the other after normal handling. The results are given in Table 111. The results obtained with Group A, flasks taken directly from their shipping containers, are probably of less significance than the others, since they represent ware in a condition which cannot be maintained in service, and since they may reflect differences in the care with which the flasks were packed for shipment. On the other hand, the results of Group B cannot be safely regarded as representing the average condition of ware in service, since no attempt was made to learn whether the average breaking temperature decreased with prolonged or rougher handling. Vycor ware was not included in these tests. Its very great resistance to thermal shock was demonstrated by heating a flask to redness and cooling it under a water tap, without its breaking.
Steam-Distillationof Small Quantities of Volatile Oils Lighter than Water FRANK M. BIFFEN Foster D. Snell, Ins., 305 Washington St., B-klyn,
T
HE method . . generally . . used to determine the amount of steamdistillable oil in a sample is to collect the distillate in B graduated cylinder or in a separatory funnel. I n the former case, the volume of oil may, if sufficient is present, he read directly; in the latter case it may he read after running off the water and collecting the oil in a graduated cylinder. Both methods are subject to serious error when only 1 or 2 ml. of oil are distilled over. Loss occurs because the oil sticks to the sides of the cylinder or funnel. A graduated cylinder of convenient size to collect the water distilled over has too large a surface area to measure the oil accurately in such small amounts. Figures 1and 2 illustrate how these defects can be eliminated by a simple combination of a graduated tube and separatory funnel.
Literature Cited (1) Federd Specification MCSOl for Chinawere, Vitrified, Section FSa and Figure 9. Washington, D. C., Superintendent of Documents. (2) Peters. C. G.. and Cregoe, C. H.. BUT.Stondordr. Sei. P a p m 16, 449 (1920): 5393. (3) Serunders, J. 8.. J . Research Nail. BUI.Standards. 23, 179 (1939); RP1227.
N. Y.
FIGURE 1
June IS, 1941
423
ANALYTICAL EDITION
Insert a graduated tube, conveniently a part of a broken buret, open at both ends, in the neck of the separatory funnel by means of a cork which has a slit to permit air to escape. The tnhe FIGURE 2 should reach nearly t o the bottom of the funnel and sufficient water he added t o cover the bottom opening. The adaptor attached to the condenser shouldlead into the top of the graduated tube. Distill in the usual manner. As volatile oils lighter than water float on the surface the bil distilled over will always remain in the graduated tube and the water will rise in the funnel. As water is cullciwd, rcnwve ~t irom tlic iunnel by OpQUiUg the stopcork, t3king cnre thnt the wawr l w p l is never heloa the bottom of the midwtte.1 tubc. Continue r h r di4lsrion until thc oil is all dL+Tilled over. This point 1s easllv found. as the volume of oil can he
Hydrolysis and Catalytic Oxidation of Cellulosic Materials A Method for Continuous Estimation of Free Glucose R. F. NICKERSON Mellon Institute, Pittsburgh, Penna.
T .
HERE are few direct methods available for the investigation of the submicroscopic structure of cellulose and,
as a result, the elaboration of essential information on the natural fibers and industrial cellulosic products has been retarded. X-ray methods are restricted to the crystalloid fraction, and copper reduction tests indicate relative amounts of chemical degradation a t the molecular level. Dispersions of cellulose, such as in cuprammonium hydroxide, reflect the properties of the dispersed unit rather than the antecedent structure. I n this paper a new method of investigation is presented and discussed, based upon the observation that quantitative hydrolytic breakdown rates of cellulose in solutions of acid can be estimated continuously and interpreted in terms of structure. Several recent articles have dealt with the evolution of carbon dioxide from simple supam, polysaccharides. uronic acids. and ~~~~~~
~~
atmosphere of nitrogen, ogtaining yidds of about 0.38 per cent carbon dioxide from pure glucose and about 0.17 Der cent from purified, p+rrxle-frrc-cottoi ccllulosc. ‘l’lsy rhocrd, also, t i m t w i t h proprr mntrol tlic rntcs arc rcproduciblc. Sickcrson 311d l.caDe fiil uzrd nir as the mrrirr m s a d O ~ S F X V Qsrirall ~ urd fairiv u h i h n amounts of oarban dioxide from purified cottons of Various other cellulosic materials have been examined. According t o Whistler and eo-workers (7), glucose, viscose and cuprammonium rayons, and cellulose acetate corrected for its acetyl content yield carbon dioxide at similar, constant rates; purified cotton, however, is characterized by a much lower rate. These carbon dioxide data were reported as percentages based on the weight of starting material. Whistler’s data could have been calculated in terms of moles rather than unit weights. As the capacity of glucose and its polymers to yield carbon dioxide must depend rimarily on certain carbon-oxygen linkages of the glncose resiiuue, it is apparent that equal weights of glucose and anhydroglueose (cellulose) would not represent eompmrahle units;
a unit weight of cellulose contains about 1.11 weights of glucose.
Thus Whistler’s figures for glucose, the regenerated celluloses,
and the cellulose fraction of cellulose acetate appear to be similar, hut, on the basis of equivalent weights, glucose would exhibit a 10 per cent greater rate of evolution than the regenerated and substituted ceiluloses.
The somewhat smaller, true evolution of carbon dioxide from cellulosic materials suggested that at least two reactions might be involved. The first reaction might be a rapid hydrolysis to glucose; the second, a slower oxidation of the glucose to an unstable intermediate product which decomposes and yields carbon dioxide. If, then, the second step could be accelerated and kept in pace with the hydrolysis, carbon dioxide evolution rates might provide data on the breakdown rates of celluloses. A method based upon this mechanism has been evolved. It was necessary as a first step to determine whether or not the carbon dioxide output from glucose could he increased and controlled. Preliminary experiments indicated that 9 per cent hydrochloric acid would be more satisfadory for the present investigation than 12 per cent. Other exploratory work led to the temporary selection of 0.5 molar as a suitable concentration of salt catalysts. The reasons for these choices are discussed in the subsequent sections.
Catalyst It appeared that the oxidative process would be simplified if complicating oxygendonator groups, such as chromates and sulfates, were avoided. Accordingly, the study of catalysts was restricted to the chlorides of metals, which were used at 0.5 M concentration in 9 per cent hydrochloric acid with pure glucose (Merck’s c. P. anhydrous dextrose) as the oxidizable substance. The catalytic activities of several salts are given in Table I.
