Detection of Destructively Distilled W o o d Turpentine In O t h e r Kinds of Turpentine by Means of the Aniline Point SIDNEY R. SNIDER AND HAROLD N. BURSTEIN of Distribution, War Food Administration, U. S. Department of Agriculture, Washington, D. C.
Naval Stores Section, Cotton and Fiber Branch, Office
The presence of destructively distilled wood turpentine in gum spirits, and perhaps also in rteam-dirtilled wood turpentine, may be detected b y aniline point tests on the high-boiling fraction distilling above 170" C., described in this paper.
FOUR
kinds of turpentine are recognized under the Federal Naval Stores Act-gum spirits of turpentine, steam-distilled wood turpentine, sulfate wood turpentine, and destructively distilled wood turpentine. The first three are produced by processes in which the oleoresin from which the terpene constituents are derived is subjected to relatively low temperatures (in the presence of a large amount of water vapor), whereas in the destructive distillation process much higher temperatures are used to effect the dry decomposition of the wood. These high temperatures in the dry distillation process result in the formation of various complex hydrocarbons and oils, some of which are closely related to the aromatic or benzene hydrocarbons, and some are perhaps of unknown identity. Destructively distilled wood turpentine usually sells a t a price below the established market price for gum spirits of turpentine or steam-distilled wood turpentine. The price differential has a t times induced unscrupulous dealers to adulterate gum spirits and steam-distilled wood turpentine by adding small quantities of the destructively distilled wood turpentine, The sale of mixtures of this kind in interstate commerce is injurious to commerce in naval stores and prejudicial to the sale of pure turpentine, and is therefore prohibited by the Federal Naval Stores Act. The wholesale price of sulfate wood turpentine is also usually below that of the other two kinds; consequently, its adulteration would hardly be economically feasible. This type of adulteration can usually be detected, especially by a person experienced in the testing of turpentine, because of the characteristic odor of the adulterant. However, to provide legally acceptable evidence, the analyst needs some method of evaluation based on scientific fact or recordable data-entirely independent of the personal element based on a sensory observation-on which to support his findings. As indicated by the standard specifications under which the several kinds of turpentine are produced and sold, destructively distilled wood turpentine contains appreciable quantities of constituents distilling in the range from 170" to 180" C. (1; 4 ) , whereas in gum spirits and steam-distilled turpentine (1, 3) which consist chiefly of CY- and @-pinene,these higher boiling constituents are present in only relatively small quantity. Another difference between destructively distilled and other types of turpentine owing to the difference in composition, is the greater so-called "solvent power" of the former. The two most commonly used methods for evaluating the solvency of paint thinners are the kauri-butanol (6) and the aniline point tests (6). The kauri-butanol test is subject to wide variation due to difficulty in temperature control, and each new solution of kauri gum must be standardized to establish reference points. The aniline point test, on the other hand, is relatively simple, is the only commonly used solvency test in which close temperature control is not a factor, and is widely used to evaluate paint thinners and diluents. (The aniline point of a diluent or solvent is the minimum equilibrium solution temperature for equal volumes of ani-
line and the solvent.) It was, therefore, considered by the authors that these two differences in properties might serve as a means of proving the presence of destructively distilled wood turpentine in other kinds of turpentine. No reliable method of detection based on chemical reactions or phenomena has as yet been found. A preliminary study of the aniline points of authentic samples of the various turpentines from widely separated sources gave the following results: g u m spirits (24 samples), 12.2" to 14.5" C.; steam-distilled turpentine (11 samples), 19" to 25.5" C.; sulfate wood turpentine (2 samples), 15" and 18" C.; destructively distilled turpentine (4 samples), all below 10" c.
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In the initial stage of this study, six samples of pure gum turpentines were fractionated and aliquots collected on a volu-
metric basis, without reference to the distilling temperature. Similar fractionations were made on these turpentines containing 5 and 10% of added destructively distilled wood turpentine. The aniline points of the various fractions from the adulterated turpentine were not sufficiently different (lower) from those of the pure turpentine fractions to permit any definite conclusions. After several preliminary tests, fractionations were made on single 1-liter samples of a pure gum spirits, a steam-distilled, a sulfate, and a destructively distilled wood turpentine, using a 250-mm. Vigreux fractionating column. The fractions were collected as follows: below 160" C.; from 160" to 163" C.; 163" to 167" C.; 167" to 170" C.; and all distilling above 170" C. (With smaller samples a 150-mm. column would be more suitable.) The aniline points of the fractions obtained by this type of separation showed that there was enough difference between destructively distilled turpentioe and the other kinds to suggest that this test might serve aa the basis for a method for positive identification or proof of its presence in a suspected mixture. Table 1. M i x e d Aniline Points of Fractions of Destructively Distilled Wood Turpentine, Collected Above 170" C. Mineral S irita (60' C., 1.P.)
7
1
c.
% 0 10 20 30 40 50
Yield of distillate over 170' C., %
Sample Number 2 3
c.
c.
4
c.
