S e p t , 1921
T H E J O CR-YAL OF 1-YUCSTRIAL AAITDENGISEERIlVG CHEMISTRI'
791
The Detection and Estimation of Coal-Tar Oils in Turpentine'
.
By V. E. Grotlisch and W. C. Smith L C i T H E R AND P A P E R
LIBORI~OXT, BCRE1U
OF CTIDYISTRI,
The detection of small quantities of coal-tar oils, such toluene, xylene, and commercial solvent naphtha, in turpentine, and the estimation of the quantity of slich adulterants present are considerably more difficult than the detection and estimation of mineral oil adulterants. Marcusson2 and Krieger3 have published methods for such analyses, but these have not, in the hands of the authors, when followed most carefully, given concordant o r reliable results, especially when the quantity of adulterant present was less than 1 0 per cent, as is frequently the case when coal-tar oils are used to adulterate turpentine fraudulently. Authentic pure gum turpentines have given results when treated according to the above methods which indicated adulteration, and samples of turpentine adulterated with as much as 2.5 and 5 per cent of solvent naphtha gave results quite similar to those obtained on pure turpentine. A brief outline of the methods referred to above may not he out of place. Marcusson adds 10 cc. of the turpentine, drop by drop, to 30 cc. of fuming nitric acid which has previoudy been cooied to -110" C. by placing the flask in a freezing mixture t,o prevent explosion or ignition of the mixture, as the reaction is extremely violent. Bft,er standing at room temperature for about 15 min., 75 cc. of ordinary concent,rated nitric acid are ndded, and the mixture is poured into 150 cc. ol water in a flask having a narrow, graduated neck and allowed to st,and on the steam bath for 15 min. The insoluble nitranion product, which settles t o the bottom, is then float,ed into the neck of t,he flask by adding concentrated sulfuric acid t,o increase the densit,y of the liquid. The volume of the nitration product, multiplied by an empirical factor, represents the quantity of coal-tar oil present, in the turpentine. Pure turpentine, according to the author, yields nitration products which go into solution in the water almost completely when heated on the steam bath, leaving only a negligibly small quantity of light reeinous residue, which cannot be confounded with the heavy oily liquid nitration product obtained from the coal-tar oils. These results are at variance with our obserrations. MTe have repeatedly obtained a considerable quantity of a viscous, gummy nitration residue from pure gum turpentine, which was insoluble in hot water, and the residues obtained in the case o f authentic turpentine adulterated with commercial solvent naphtha to the esteiit OP 3. 5. and 10 per cent, respectively, were all of 1-ery nearly the same volume as that obtained from pure turpentine, the only difference being a diminution of viscosity as the percentage of aclulterant present increased. The 10 per cent residue was not free-flowing, and could not be called liquid. Krieger shakes 20 cc. of the turpentine with 100 cc. of diluted sulfuric acid (4: 1, sp. gr. 1.76) in a fl-slr, dilutes wlth 200 cy. sulfuric acid (4 : 1, sp. gr. 1.76) in a flask, dilutes with 200 cc. of water, and distils with steam. This is repeated, and the oily portion of the final distillate, which is supposed 40 represent total aromatic and paraffin hydrocarbons, 1s treated with 10 t o 15 cc. of fuming sulfuric acid containing 8 per cent free SOa, t o sulfonate the benzene hydrowhich separates is considered a s mineral oil, and the difference between the volume of this oil and the volume of the oily distillate obtained by the last steam distillationis calculated as benzene or coal-tar hydrocarbons. As shown by Veitch and Donk,d it requires a fuming sulfuric acid, containing approxiniately 4 per cent free SO.. in the proportion of 4 parts acid to 1 part turpentine. to-
ab
1 Presented before t h e Dii-ision of l m d a r r i a i and Engineering Chemistry a t t h e 61st Meeting of t h e American Chemical Fociery, Rochester, K. T.. April 26 to 29. 1971.
2 C h e m . - Z t g , 36 (1912),413. 4'21. I b i d . , 40 (1916),95'7: J . ROC. Chem. I n & . 35 (19161.7 4 6 G . 4 C . Y. Bureau of Chemistry. Circula: S i .
c.s.
I)LPARTJfElrT Or . i G R I C L L T C R E ,
WASHlhGlOS,
D. C.
gether with heating and frequent agitation a t BOo to ti5" C. for 1 0 min. to polymerize pure turpentine completely. Even then, on addition of ordinary concentrated sulfuric acid ancl steam distillation of the mixture, a small percentage (below 5 per cent) of a dark volatile oil with unpleasant odor, is oiten recovered, having a refractive index above 1.500. It is thus evident that turpentine cannot be completely polymerized by Krieger's method, and that the steam distillate will contain more or less terpene hydrocarbons. Such was found to be the case. I n order to be able to detect nith certainty small perceiitages of coal t a r oils, i. e.,, 1 or 2 per cent, it was deemed necessary first to concentrate these oils from a large 1 olunie of sample. Fractionation was not feasible, as most solvent naphthas have initial distilling temperatures below that of turpentine, with a much wider clistillation temperature range. It was found that the reaction between turpentinr and dry hydrogen chloride gas offered a solution to this phase of the problem. The pinene hydrochloride crystallizes out on stancling in the cold, and the non-crystallizable products have much higher boiling points, while both coaltar oil and mineral oil are unaffected. On filtering o b the crystalline pinene hydrochloride and distilling the filtrate under reduced pressure, the coal-tar oils are all concentrated in the first portions of the distillate. By sulfonating this distillate with fuming sulfuric acid, the terpenes are polymerized into soluble, nonvolatile bo~hes, and the benzene hydrocarbons are converted into sulfoiiic acids. If the mixture is then subjected t o steam distillatioii, a very small percentage of volatile oil, having a dark yellow color, disagreeable odor, and a refractive index at 20" C slightly above 1.500, IS reco~7ereci in the case of pure turpentine. Lf any niineral oil is present, it is recovered at this stage as a limpid, almost colorless oil, hajing the characteristic mineral oil odor ancl a refraetive index below 1.500, usually below 1.480. Pure toluene, xylene. and solveiit naphtha give no oily distillate when the sulfonation mixture is steam distilled. The coal-tar oils which are recorrred, after the steam ilistilIalioii no Ionger give any oiIy distillate. by the reaction first pointed out by drnistroiig and Miller,l -who showed that if the sulfonic acids of the benzene hydrocarbons, dissolved in an excess of sulfuric acid, are heated in the presence of steam to temperatures above 100" C., depending on the hydrocarbon derivative used, clecomposition takes place with liberation of the free hyclrocarbon. The operation is carried out by adding water, drop by drop, to the boiling acid mixture. The oils recovered in this step have always had practically the same odor and refractive index a s the original coal-tar oil used as the adulterant. The recovery of any appreciable quantity of oil at this stage is an indication of the presence of coal-tar oils in the turpentine under examination. The resuWPobtained by the proposed method are given in Table I. I t will be noted from this table that traces O T oil are usually recovered in the case of pure gum turpentine. However, the small.quantity of such oil recovered from pure turpentine, its odor, and the resinous gummy product obtained upon nitration, as outlined more fully below, serve to distinguish between this oil and that obtained when even small quantities of coal-tar oils are present. It was impossible to recover the theoretical quantity of coal-tar oil which was added to the turpentine in the es: d . Chem.
Eoc.. 43 ( l S M ) , 150.
T H E J O C ' K N A L O F INDUSTRIAL d N D E N G I N E E R I N G C H E M I S T R Y
792
TABLE I S11mple
No.
OBTAIXED
--BnStiLTS
Adulterant P r e s e n t Ejeture of SamDle
P e r cent 1 Pure tiirpentine. No. 1 2 No;' 1, sdtll2erate8
15 4
8
"
6 Pur0 turpentine. No 2 7 Noi, 2, a d n l y n t e d S 9 Pure turpentine, Wo. S 10 "or' 3, adUlt,pted 11 12 Pure turpantine No. 4 13 N o i c & &ddt$dd
14 15
16
O S ICNOWX M I X T U R E S OF
None
5
4.8 10 2.5 None 8 10
None 10 2 None 2 2
SO!^.
Kind nap+,tha, 'I
1
., 2
"
3
I'
3
Mineral s p i r i t s
C. P. xylene C. P toluene
a 5
perimentb. Hydrolysis of the sulfonic acids takes place very slowly at the temperature of initial hydrolysis, and requires a constantly rising temperature to bring about anything approaching a complete recovery of the hydrocarbons in a reasonable length of time. The reaction being a rcversiblc one, it was found that the recovery of the hydrocarbons was better, the more rapidlr the operation was carried out. However, when the temperature of the acid mixture row to about 1-10" C., frothing set in, due to the resinous and carbonaceous matter formed by the action of the sulfuric acid on the terpene compounds. When the frothing became excessive, it was necessary to discontinue the distillation. The use of paraffin to prevent frothing did not prove feasible, since some of it was carried over into the distillate, introducing a corresponding error in the results. An empirical factor of 2.2, by which to multiply the quantity of oil recovered to show the true quantity present, was determined by experiment, as shown in Table I. One hundred-cc. samples were used in each experiment. RECOMNENDED PROCEDURE Place 100 cc. of the turpentine in a wide-mouth, 8-oz. bottle fitted with a 2-hole stopper carrying glass tubes arranged a s in a gas-washing bottle. Allow to. stand in a mixture Df ice and salt f o r a short time, and then pass into the turpentine a gentle stream of hydrogen chloride gas, dried by passing through two gas-washing bottles containing concentrated sulfuri: acid. A sufficient quantity of gas may be conveniently generated by gently warming 100 g. of common salt with 100 cc. of sulfuric acid made u p by diluting 85 to 90 cc. of the concentrated acid. The acid is added to the salt from a dropping funnel in portions of about 20 cc. during the course of the absorption. A 3-way stopcock is placed between the generator and the Arst wash bottle, so that when the absorption of HC1 by the turpentine is complete, the gas still being generated can be diverted readily into a bottle containing sodium hydroxide solution. The tube should not extend into the solution but just into the neck of the bottle. A n ordinary 2-way stopcock is also placed between the second wash bottle and the absorption bottle, so that the former may be closed from the air while not in use. An exit tube from the absorption bottle leads into the neck of a bottle containing a little water. When the absorption of gas is complete, the excess passes on through the turpentine into this bottle, and can be seen dissolving in the water. After the absorption is complete, disconnect the absorption bottle and allow to stand, corked, in a freezing mixture for about an hour, to obtain maximum crystallization of the pinene hydrochloride. This compound is very soluble in both mineral and coal-tar oils, so that with increasinq percentages of adulteration the quantity of crystals formed becomes smaller, and scarcely any are formed at 10 per cent
Vol. 13, No. 9
GUM 'l'CI2PEXTIKES L Y D COAL-TAROILS Recovered Pro ortion of Recovered Tota? Coal-Tar on Steam on Direct Distillation Distillation Adulterant Recovered CC. cc. P e r cent Trace Trace '2 2.2 44 0.f44.4 2.0 O.LD BO 2.0 1.23 50
...
5;::
0.35 7.5
0.3
0.3 0.3 0.3 0.3 0.2 4.0
0.2 3.2
0.2 0.2 5.5
0.9 Trace 0.8
0.8
2.2
40'
.... .. 41 ... 40 55
40
44 Mean. 44.8 F a c t o r , 2.2
adulteration. Filter off the crystals on a small Hirsch funnel, with suction, and distil the filtrate under a reduced pressure equivalent to 1 0 in. of mercury, until crystals separate out in the condenser (which indicates complete distillation of the oils) or untll 25 cc, of distillate are obtained. I f the quantity of adulterant is quite large, Le., 1 0 per cent or more, as shown by the odor of the original sample, it will be well to collect a second 25-cc. portion of distillate and treat in the same way as the first, adding the results together. Add the distillate slowly with occasional shaking, to four times its voluue of fuming sulfuric acid containing 3 to 4 per cent free SO,, in an Erlenmeyer flask, keeping cool by holding under the water tap. Acid of 4 per cent free SO, content is that regularly used f o r testing turpentine for mineral oil, and contains 82.38 per cent total SO,, equivalent to 100.92 per cent total H,SO,.' After the distillate has all been added to the acid, the flask is heated on the steam bath a t about 70" C., for about 20 min., with frequent thorough shaking, in order to sulfonate the o h completely. It was found that pinene hydrochloride is not readily sulfonated, and after cooling the sulfonation mixture, crystals will sometimes appear, especially when the turpentine is pure or only slightly adulterated. If the quantity is appreciable, it is advantageous to filter off these crystals on a small Hirsch funnel before proceeding. No filtering medium is needed. Dilute the sulfonation mixture cautiously with an equal volume of cold water and pass steam through it, collecting the distillate. I n the case of pure turpentine, only a very small quantity (not over 0.5 cc.) of a disagreeably smelling, yellow, and rapidly darkening oil is recovered, having a refractive index a t 20" C . above 1.500. I f mineral oil is present, it is recovered at this point, and can be identified by its characteristic odor and refractive index, which is usually below 1.400. When oil ceases t o come over with the steam, disconnect the steam line and distil with direct heat, fitting the cork of the flask with a dropping funnel and a thermometer which extends into the liquid. After the mixture starts to boil, and when the condensate starts to show a n oily portion, allow warm water to flow from the dropping funnel down the side of the flask, a t a slightly slower rate than that at which it is being distilled off, to obtain a gradually increasing boiling temperature. Run the distillation at the rate of about 3 drops per see., or about 7 to 8 cc. per rnin. I n the case of adulteration with solvent naphtha hydrolysis starts at about 115" C. Discontinue the distillation when frothing becomes excessive, to prevent contamination of the distillate with the acid mixture. Note the quantity of oil recovered and multiply by the factor 2.2. The result will be the percentage of coal-tar oil present in the turpentine. A convenient method f o r preparing t h i s acid is described i n U. S. Department of Agriculture, Bulletin 898.
Sept., 1921
T H E J O U R N A L OF INDUSTRIAL A N D ENGINEERING C H E M I S T R Y
I f the oil recovered is less than 0.5 cc., it may be neglected, a s the quantity of adulterant, if any, is probably less than 1 per cent. Further to identify the oil as consisting of benzene hydrocarbons, nitrate a little of it by dropping cautiously into three times its volume of fuming nitric acid, previously cooled in ice water. After warming slightly and standing aside until the action ceases, pour the mixture into cold 4 heavy, yellow to light brown, aromatic smelling water. , oil separates out which, after washing away the excess acid, has a refractive index between 1.550 and 1.555 a t 20" C. The odor is characteristic of nitrobenzene and its homologs. To carry the test still further, it may be reduced with a little zinc and hydrochloric acid, and, after neutralizing with sodium hydroxide, the amines may be recovered bx steam distillation and extraction of the distillate with ether. Evaporate off the ether, acidifying with hydrochloric acid, diazotize with sodium nitrite solution, and after neutralizing with a little sodium hydroxide solution, convert into a bright scarlet azo dye by adding a few cc. of a solution of the dye intermediate known as F-acid, 2,7-/3-naphtholsulfonic acid. A piece of washed wool boiled in the solution after making slightly acid with acetic acid will be dyed a bright scarlet, fast to light. Other intermediates of the general nature of F-acid may be used, if the latter is not available, but F-acid gives the brightest solution. Wood turpentines, both steam and destructively distilled, do not give reliable results when tested by the above procedure, probably because the high temperatures to which the wood and the resinous constituents thereof are exposed in present methods of manufacture partly break down the terpenes and resins t o simple ring hydrocarbons. Both
793
toluene1 and m-isopropyltoluene, or m-isoopmne hatre bee11 identified in rosin spirits, the low-boiling fraction from the destructive distillation of rosin. The destructively distilled wood turpentines, as was to be expected, gave considerably higher yields of oil from the distillation of the sulfonatior~ mixture than the steam distilled wood turpentines. The wood in the steam distillation process, being treated with superheated steam, is not subjected to such high temperatures as to decompose the rosin materially, as in the destmctive distillation process. This is being studied further.
SUMMARY A method has been devised f o r detecting and estimating the percentage of coal-tar oils in gum turpentine adulterated therewith. The method will also serve to detect the presence of mineral oils if any be present. As a result of certain causes not fully understood, the recovery of coal-tar oils is, on the average, about 45 per cent of the theoretical, requiring that the quantity of oil recovered be multiplied by the factor 2.2. In order t o obtain concordant results, the strength of the sulfuric acid used to decompose the turpentine must be definite, varying between 3 and 4 per cent free SO,. A method for further identifying the oils obtained in the last step of the analysis has also been described. The method is not strictly applicable to wood turpentine, because small quantities of the coal-tar oils are often found a s normal constituents of this kind of turpentine. However, any considerable recovery of oil from the sulfonation mixture, Le., 4 per cent or more, even in the case of destructively distilled wood turpentine, will serve t,o throw suspicion on the purity of the turpentine.
A Revision of the Optical Method for Analyzing Mixtures of Sucrose and Raffinose' By C. A. Browne and C. A. Gamble THEKEW YORKSUGART R A D LABORATORY, ~ INC.,80
One of the most interesting sugars from a chemical and analytical standpoint is the trisaccharide, rallinose,. This sugar, first indicated by Johnston' in Eucalyptus mamma in 1843, was afterwards investigated in 1856 by Berthelot," who gave it the name melitose. I n 1876 Loiseau' discovered in the impure molasses of a beet-sugar refinery a n unknown high polarizing sugar to which he gave, from the place of its occurrence, the name raffinose. I n 1884 Bohm' announced the discovery in cottonseeds of a new sugar to which he gave the name gossypose. Tollens6 in 1886 proved melitose and gossypose to be identical with Loiseau's raffinose. This identification was important, f o r it established the wide occurrence of raffinosc in the vegetable kingdom. The sugar has been found also in young wheat sprouts, in barley, and in other plant substances; careful investigation would no doubt show it to be widely distributed. Raffinose is almost always associated in nature with sucrose, and the iniportance of devising a method for estimating these two sugars when they occur together was 1 Presented before the Section of Sugar Chemistry and Technology at the 61st Meeting of the American Chemical Society, Rochester, h'. Y., April 26 to 29, 1921. * J. prabt. Chem., [l] ag (1843),485. Ann. Chzm., [31 46 (1856), 66. 4 Compt. rend., 82 (1876), 1058. 5 J. prakt. Chem., [ Z ] 30 (ISM), 37. ' Ann., 232 (1886), 169.
EOUTH ST..NE,&YORH,S . T.
quickly recognized, especially in the analysis of beet sugars, where the presence of only a slight amount of raffinose may cause the polarization of a sugar to exceed 100. Owing to the fact that raffinose is hydrolyzed by the ordinary methods of acid inversion and undergoes a decrease in polarizing power, the customary Clerget method for determining suc1"ose was found t o be no longer applica,~ found ble t o sucrose-raffinose mixtures. C r e ~ d t however, that when a separate formula f o r estimating raffinose IS united with the familiar Clerget formula, a combined eqnation can be derived which permits the estimation of the two sugars with a f a i r degree of accuracy. With the later substitution of the Herzfeld modificatioa in place of the old Clerget process of inversion, the Creydt formulas for estimating sucrose and raffinose were revised in order to conform to the new conditions. These revised formulas, a s given by H e r ~ f e l d ,a~r e 0.5124 P-I" 0.3266 P+P'
s=--
and R0.330 1..554 in which S and R are respectively the percentages of SUcrose and raffinose, and P and P', respectively, the direct and invert polarizations at 20°C.
1 Pelletier a n d Walter, Aflfl. r h m . phys., Kelbe, Ann., 210 (1881), 14. 2 Kelbe, LOC.cit. 3 Z. Ver. deut. Zrekerind., 37 (188i), 153. 4 Z T'er. deirt Zrirk~76n-d~ 40 (lRW), 193
[21, 6 i (-),
2iS;
