Nomograph for Iodine Value of Tung Oil C. S. WAN
AND
K. HO, Chemical Research Laboratory, Government Testing Bureau, Hankow, China TABLEI. COMPARISON OF IODINEVALUESCORRECTED BY NOMOGRAPH AND FORMULA
T
HE iodine value of tung oil as determined by the Wijs method is greatly affected by time of contact, excess of Wijs reagent, and working temperature. These factors have been extensively studied by Ho, Wan, and Wen ( I ) , who have developed the formula log Yt = 0.001672 (t
Experimental D a t a Exceas of
iodine, CP./IC.
Iodine value
20.00 c. 160.2 163.6 168.2 164.2 191.2 165.5 218.8 166.5 169.3 266.8 169.0 270.0 169.9 333.4 350.0 171.3 26.3' C. 169.0 165.2 183.7 167.0 208.3 167.2 210.8 167.8 266.5 170.5 281.6 171.1 350.4 172.4 29.20 c. 158.3 165.4 166.1 166.6 169.2 166.2 168.0 202.3 169.0 221.0 171.8 273.4 172.3 289.8 173.3 318.8
+ 10.56)(10g2(t/"9 X - 2.15) 4X 0.0008625 + B
(1) where Yt = iodine value at working temperature, t t = working temperature in O C. X = excess of Wijs reagent in cg. of iodine per gram of oil B = characteristic value of individual oil sample
_I
32.OoC.
165.1 154.1 165.5 154.2 167.0 181.0 167.6 181.2 168.7 211.2 170.1 223.5 279.6 172.0 297.5 173.1 35.6' C. 167.3 154.7 169.0 179.4 170.3 211.5 173.1 236.0 173.6 263.0 176.0 298.7 38.6' C. 161.4 168.2 177.7 169.6 195.4 170.8 216.6 171.9 267.0 175.7 276.8 175.8
180
I90
.m 210 0 220
Iodine Iodine Value Value Nomograph Corrected Calculated Correoby by tion NomoeraDh _ . Formula 1.3.8 4-3.4 f2.3 +1.1 -0.6 -0.7 -2.5 -2.9
167.4 167.6 167.8 167.6 168.7 168.3 167.4 168.4
167.4 167.6 167.8 167.6 168.7 168.3 167.4 168.4
0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
+2.3 +1.4
+o.
Difference
0.0 0.0
1
0.0 -2.4 -3.0 -5.3
0.0
0.0 0.0
4-2.4 4-1.8 1-1.7 -0.3 -1.3 -3.7 -4.4 -5.4
167.8 167.9 167.9 167.7 167.7 168 1 167.9 167.9
167.8 167.9 167.9 167.7 167.7 168.0 167.9 167.8
0.0 0.0 0.0 0.0 0.0 $0.1 0.0 $0.1
f2.1 +2.1 4-0.2 f0.2 -1.7 -2.4 -5.1 -5.8
167.2 167.6 167.2 167 S 167.0 167.7 166.9 167.3
167.2 167.6 167.2 167.8 167.1 167.7 166.9 167.3
0.0 0.0 0.0 0.0 -0.1 0.0 0.0 0.0
+1.1 -0.8 -3.0 -4.4 -5.9 -7.6
168.4 168.2 167.3 168.7 167.7 168.4
168.4 168.2 167.3 168.7 167.7 168.4
0.0 0.0 0.0 0.0 0.0 0.0
-0.5 -1.8 -3.2 -4.6 -7.6 -8.1
167.7 167.8 167.6 167.3 168.1 167.7
167.7 167.8 167.7 167.3 168.1 167.7
0.0 0.0 -0.1 0.0 0.0 0.0
3
In order that the iodine values of tung oil determined in different l a b o r a t o r i e s can be readily compared, they have proposed to use 250 cg. excess of iodine and a time of contact of 1 hour a t 20' C. as common standard conditions. Under the proposed standard conditions, Equation 1 is simplified as follows:
+
log Y = 0.0161 B (2) where Y = iodine value at proposed standard conditions B = characteristic value of individual oil sample
\38
320
330
40
340 350
FIGURE1 282
Before making use of Equation 2, one has to calculate the value of B by means of Equation l. The calculation, though not very difficult, is rather complicated and requires much time. The authors, after carefully studying the relations, have worked out a n o m o g r a p h , f r o m which one can read off the correction and consequently obtain the iodine value a t the proposed standard conditions without going through comprehensive calculation.
a
283
ANALYTICAL EDITION
JULY 15, 1936
If a straight line is drawn from a particular excess of iodine and working temperature of the experiment, it will intersect the correction scale. When the correction indicated on this scale is applied to the iodine value obtained experimentally under laboratory conditions, one gets directly the iodine value at 250 cg. excess of iodine and 20" C. It is understood that the time of contact is to be exactly 1 hour. Example Oil taken, 0.1505 gram Sodium thiosulfate in blank titration, 46.86 CC. Sodium thiosulfate used for the test, 26.61 cc. Difference, 20.25 cc. Strength of sodium thiosulfate solution, 1.264 cg. of iodine per cc. 20'25 X 1.264 = 170.1 Experimental iodine value, 0.1505 26 61 Excess of iodine, 170.1 X -= 20.25 223.5 cg. of iodine per gram of oil
Working temperature, 32" C. Time of contact in the dark, 1 hour When 223.5 on the excess scale and 32 on the temperature scale in the nomograph are joined by a straight line, the line will intersect the correction scale at -2.36. The iodine value at the proposed standard conditions is then equal to 170.1 - 2.36, or 167.7, which checks very well with the value calculated by the formula. The authors have carefully checked the data contained in their previous article (1). The iodine value calculated with their formula and those read off from this nomograph are tabulated together in Table I for comparison.
Literature Cited (1) Ho, K., Wan, C. S., and Wen, S.H., IND.ENG.CHEW,Anal. Ed., 7, 96-101 (1935). RJCEIVED February 20,1936. Published with the permission of C. Y. Wang, Commissioner of Government Testing Bureau, Ministry of Industry, Hankow, China.
Quantitative Determination of 5-Methyl Furfural HAROLD A. IDDLES AND KENDRICK S. FRENCH, University of New Hampshire, Durham, N. H.
I
N T H E production of furfural by the distillation of various
pentose- and pentosan-containing natural products with mineral acids, i t would be expected that any methyl pentoses and methyl pentosans would yield 5-methyl furfural in an analogous manner and the polysaccharides which hydrolyze to hexoses would give rise to small amounts of p-hydroxy &methyl furfural. The effect of these compounds, particularly 5-methyl furfural, on the quantitative determination of furfural was first studied by Votocek (18), who prepared a pure sample of 5-methyl furfural from rhamnose, with which precipitations with phloroglucinol were carried on to determine the ratio of product t o aldehyde employed. Later Ellet and Tollens (5) studied the relation between the quantity of phloroglucinol precipitate and the amount of rhamnose employed as a test sample in hydrochloric acid distillation. Fromherz (6) determined the furfural and methyl furfural in samples of wood by the production of the phloroglucides with a subsequent attempted separation of the mixed precipitate by using the alcohol solubility of the phloroglucides of 5-methyl furfural. Dox and Plaisance (3) questioned the reliability of this alcohol separation of the phloroglucides and recorded in their work the qualitative reaction of thiobarbituric acid with 5-methyl furfural but gave no quantitative data because of the limited amount of material on hand. Since it is now possible to prepare pure 5-methyl furfural in quantity according to the directions of Rinkes (Id), it seemed desirable to make a comparative study of the various gravimetric and volumetric methods for the determination of furfural when applied to pure 5-methyl furfural itself. In this direct study it is possible to eliminate the variables introduced when the calculations refer back to an original methyl pentose or methyl pentosan sample which has undergone an acid distillation. The methods selected for study were the phloroglucinol or A. 0. A. C. method (I), the thiobarbituric acid method (3,10, 17, 19), the 2, 4-dinitrophenylhydrazine method (8, IS), the volumetric bromidebromate titration method (2, 4,10-13,15), and the volumetric bromide-bromate titration a t 0" C. ( 7 ) .
Preparation of 5-Methyl Furfural The 5-methyl furfural was prepared according to the method of Rinkes (14)in which levulose, produced by acid hydrolysis of sucrose, is dehydrated to produce pchloro5-methyl furfural and the chlorine is replaced by hydrogen
by means of stannous chloride reduction. The resulting product was vacuum-distilled at 75" to 76" C. and 13 mm. pressure, yielding clear samples for analysis which showed a I L D (Pulfrich) of 1.53049 a t 20" C., and 1.52643 a t 25" C. G r a v i m e t r i c Methods PHLOROGLUCINOL METHODAND METHODOF CALCULATION. In the procedure as finally developed, a weighed sample of the pure redistilled 5-methyl furfural was diluted to 1 liter with distilled water and 5-, lo-, or 15-ml. aliquot portions were drawn from a buret into 200 ml. of 12 per cent hydrochloric acid solution. To this was added 0.33 gram of phloroglucinol in 50 ml. of 12 per cent hydrochloric acid solution, a quantity which is in excess of the amount necessary for the 5-methyl furfural present. After waiting 8 to 10 minutes for precipitation to begin, the solution was diluted to 400 ml. using 12 per cent hydrochloric acid and allowed to stand 16 t o 20 hours in the dark. Finally the precipitate was collected on a tared Gooch crucible, washed with 150 ml. of cold water, and then dried in a vacuum desiccator over a dehydrating agent to prevent the darkening and decomposition caused by drying in the oven at 100' C., ohich is the practice with furfural. I n the work of Fromherz (6) the ratio of the weight of precipitate to the weight of sample increased with the size of sample used. To substantiate these results, a series of determinations was made, using samples varying from 0.018 to 0.132 gram to determine the effect of sample size on the ratio of precipitate to sample. TABLEI. EFFECTOF SAMPLE SIZEON RATIOOF PRECIPITATE TO SAMPLE Weight of Sample Oram
0.0180 0.0226 0.0265 0,0451 0.0529 0.0541 0.0677 0.0794 0.0902 0.1058
Weight of Precipitate
Weight of Precipitate Weight of Sample
Cram
0,0182 0.0270 0.0345 0.0745 0.0897 0.0917 0.1201 0.1468 0.1686 0.2019
1.012 1.194 1.302 1.652 1.696 1.686 1.774 1.849 1.869 1.906
It can be seen from Table I that the ratio tends to increase regularly with the size of sample from 1.012 to 1.905. This increase may be explained by considering the solubility of precipitate to remain constant in the constant volume of
