Vol. 19, No. 7
INDUSTRIAL AND ENGINEERING CHEMISTRY
826
Note on Two Natural Resins' By F. H. Geake GOVERNMENT LABORATORY, BANGKOK, SIAM
T
WO new resins of vegetable origin have been examined
with a view to their possible commercial utility in American and European markets. The resins are at present exported in small quantities from the port of Chantaburi in southeastern Siam, and, mixed with others under the general trade name of "Damars," find a limited application locally. Both resins are derived from Dipterocarpaceous trees. That designated below as A is from a tree known locally as Chan. No flowering specimen has yet been found and the tree has therefore not been definitely identified. The resin designated as B is from a tree known locally as Yang Panawng. It has been identified as a Shorea, near Shorea hypochra, Hance. Both trees are found in considerable quantities in the Chantaburi Province of Siam. Resin A has a light brown color. The sample examined was in fairly large, nearly opaque lumps. The resin was fairly clean, but contained a certain amount of foreign veyetable matter. Resin B is of a very pale yellow color, and nearly, transparent. Analytical Data
The principal characteristics of the resins are shown in Table I and were obtained by the usual methods. The data for resin B are similar to those frequently exhibited by Damars.
distillation with steam: resin A , 0.3 per cent; resin B, nil, The oil obtained from resin A was yellow, viscous, an& soluble in alcohol and ether, Solubility in Various Solvents
The solubility of the resins in several solvents has been determined quantitatively (Table 111). Table 111-Solubility
Ether Oil of turpentine Linseed oil Benzene Water Petrol ether Chloroform Carbon tetrachloride Alcohol-ether ( 1 : l ) Alcohol-benzene (1:l) Alcohol-oil of turpentine (1:l) Acetone Aniline oil ~~~~~
~~~~
~
in Various Solvents RESINA RESINB Per cent Per cent 61.6 84.5 99.9 98.4 1.4 23.0 Nearly complete 96.1 51.2 67.8 93.0 Partial ' Nearly complete
Resin B is remarkable for its almost complete solubility in a very wide range of solvents. Varnish Tests
The softening points and melting points were determined on the ground resins. The softening point was taken when the particles appeared to be starting to coalesce, the melting point when a definite meniscus was formed. The hardness of the resins is considerably influenced by temperature. Resin A is harder than B.
The utility of a resin to the varnish maker can only be ascertained by trade tests. A few tests, however, have been conducted on a laboratory scale and some of the results may be of interest. Varnishes have been prepared from resin A by fiolution in alcohol, benzene, and oil of turpentine. The alcohol and benzene varnishes are of good color and luster and dry rapidly. The finished varnishes are not sticky and show no tendency to grain after 8 months. They are not affected by moisture and will stand exposure to the sun. They are similar in appearance to kauri varnishes and seem to be a t least equally satisfactory. The oil of turpentine varnish is somewhat darker and of poorer luster, but is equally resistant to atmospheric conditions and does not grain. Varnishes have been prepared from resin B in the same solvents. They are somewhat darker than the resin A varnishes, but show no tendency to grain.
Solubility in Alcohol
Dry Distillation
Keither resin is completely soluble in alcohol, and both would, therefore, require some pretreatment before being used for the preparation of spirit varnishes. The acid value and Kottstorfer number of the alcohol-soluble portions of the resins are given in Table 11. It is a matter of common experience that the solubility of resins in alcohol is frequently increased on "melting." The figures in Table 11, however, show that this is not the case with the resins under examination.
On dry distillation resin A yielded a pale, fluorescent green oil. The temperature of distillation rose rapidly t o 260" C., and then more slowly to 320" C. A considerable residue of dark green pitch was left. T6e acid value and Kottstorfer number are given in Table IV. Sixty-two per cent of the resin passed over as oil. Resin B yielded an oil of a pale amber color, later becoming greenish. Definite boiling points seemed to be established temporarily at 258" and 282" C., and the oil could probably be readily fractionated. One per cent of the oil passed over below 150" C. and 75 per cent above, the maximum temperature reached being 356" C. The acid value and Kottstorfer number of the oil are given in Table IV.
Table I-Analytical Density Acid value Kottstdrfer number Per cent moisture Per cent ash Softening point, C. Melting point, C. Hardness (29.2 C.)
Characteristics RESINA
but not copper sulfate
RESINB
but not copper sulfate or calcite
Characteristics of Alcohol-Soluble Portions of Resins Ressw B RESINA Solubility of untreated resin (95 per cent alcohol), ner 77.4 r _ _rent 49.3 77.1 Solubility after melting, per cent 41.0 25.9 55.7 Acid value of alcohol-soluble portion 10.5 47.2 Kottstorfer number of alcohol-soluble portion T a b l e 11-Analytical
____
Products of Steam Distillation
Keither resin yields an appreciable quantity of volatile oil. The following yields of volatile oil were obtained by 1
Received March 8, 1927.
Table IV-Analytical Density Acid value Kottstorfer number
D a t a on Products of Dry Distillation RESINA RESINB 0.953 0.943 2.1 2.7 7.4 16.4
The distillation properties and analytical characteristics of both oils were quite different from th0.e of rosin oil
8
July, 1927
IXDUSTRIAL AiVD ENGINEERING CHEMISTRY
a n d they could not, therefore, be used as a substitute for it. They are not suitable for lubrication purposes, except perhaps for cold bearings. Summary Two new resins from trees growing in southeastern L’3’lam have been investigated. Neither resin i i completely soluble in alcohol and the solubility is not improved by “melting.” Neither resin yields an appreciable quantity of essential oil. Both resins give varnishes with alcohol, benzene, and oil
827
of turpentine, which may be of some commercial value. That designated A seems to be equal in quality to kauri. Both resins yield oils on dry distillation, which, however, do not resemble rosin oil, and are not likely to find immediate commercial application. Acknowledgment The author’s thanks are due to His Royal Highness the Prince of Kambaeng Bejra, Minister for Commerce and Communications, Siam, for permission to publish this note, and to A. Marcan and to Dr. Kerr for much valuable advice and assistance.
Data on the Assay of Rolled Gold Plate’ By Raleigh Gilchrist NATIONAL BURBAUOB STANDARDS, WASHINGTON, D. C.
HE assay of articles of jewelry, such as watch cases, rings, lockets, stickpins, ornamental and emblematic buttons, lavalieres, coverings for knife handles, etc., presents a number of problems. Such articles are sometimes made of solid gold--that is, they are made up entirely of a gold alloy. Another class consists of articles composed of base metals which have been plated with pure gold either electrolytically or by “dipping,” and articles which have been electroplated with gold alloy. Probably the largest proportion of gold jewelry, however, consists of base metal partially or completely covered with a layer of gold alloy considerably thicker than is usually applied by plating Such articles are made from stock rolled or drawn from billets consisting of base-metal alloy and gold alloy which have been brazed or soldered together. In some cases, as with rings and chains, the gold alloy completely surrounds a core of base metal. I n flat pieces or pieces fashioned from sheet, one or both of the principal surfaces may be covered with gold alloy. Certain types of such articles are known in the trade as filled gold, while others are called rolled gold. The terms are not clearly distinguished. Rolled gold is known as single plate when only one side is covered with gold alloy, and as double plate when both principal surfaces are covered. The assay of rolled gold articles may involve simply a determination of the total gold content of the entire article. Such an assay does not present any unusual difficulty. Generally it is desired to know the fiheness of the gold alloy together with its thickness or its proportion by weight. The thickness may be determined by means of a photomicrograph of a cross section of the specimen or, by direct measurement of the stripped alloy with a micrometer caliper (with ratchet head) graduated to 0.0001 inch (0.0025 mm.). The latter method is not capable of such great precision as the former and is only applicable to approximately flat specimens. However, the method is much more rapid and the results are sufficiently precise in many cases. The values obtained are probably reliable to 0.0001 or 0.0002 inch (0.0025 or 0.0050 mm.). One advantage is the possibility of averaging a number of measurements, thereby compensating for the lack of uniformity in the thickness of the gold-alloy layer. The determination of the fineness of the gold alloy or its proportion by weight to that of the entire article requires that the gold alloy be separated from the base-metal alloy. In
‘T
1
rector
Received February 16, 1927. Published by permission of t h e DIhTational 13ureau of Standards.
the first case it would not be necessary to remove the gold alloy completely but only to take a sample. If this could be done by mechanical means as by a milling cutter the subsequent assay would be simple. However, this method is practically barred by the uneven contour of most specimens and by the fact that the layer is usually not thick enough, seldom exceeding 0.003 inch (0.076 mm.).z The method commonly used is to remove the base-metal alloy by means of a stripping solution. The effect which such solutions may have upon the gold alloy would fall within the limits of accuracy ordinarily required for the determination of the weight of the alloy. However, the action of the stripping solutions may introduce certain errors which would have an appreciable effect upon the determination of the fineness of the alloy. These errors may be summed up as follo\vs : 1-Since the gold-filled stock is made from a gold alloy which has been brazed or soldered to a base-metal alloy, there exists a t the junction of the two dissimilar alloys a region in which the proportion of gold varies from that of the gold alloy proper t o zero. This region may be attacked to a greater or lesser extent, leaving i t either richer or poorer in gold than the.main alloy. That there is a differential solvent action at the junction is made evident by the fact that this surface is always black. A portion of this blackened surface is loosely adherent and may be readily removed. The extent to which this material is removed in preparing the sample for assay might affect the determination. 2-The stripping solution may have a solvent effect upon the gold alloy. This solvent action may be differential in character.
The effect of these two factors would vary with the thickness of the gold alloy. Similarly the effect of the two factors mentioned would yary with the temperature at which the solution is maintained. JtThen the writer recently was called upon to test a number of samples of rolled-gold plate (mainly single plate) it was found that the literature contained no data 011 the effect ’ 2 Federal Trade Commission, Trade Practice Submittal on the GoldFilled Watch Case Industry, January 18, 1923. “As a result of consultations between the Federal Trade Commission, Washington, D. C., and manufacturers of gold-filled a n d gold-plated watch cases, representing approximately 75 per cent of t h a t industry, specifications were adopted requiring t h a t the fineness of the gold alloy used in gold-filled cases shall not be less by more t h a n three one-thousandths p a r t than t h e fineness indicated, t h a t t h e sheet of gold or alloy affixed t o t h e outer surface of the backs, center, open face bezel, pendant, crown a n d bow shall not be less t h a n three one-thousandths of a n inch in thickness a n d t h a t the sheets of gold or alloy affixed to t h e inner surfaces of t h e backs, t o t h e inner and outer surfaces of the caps a n d t o the outer surface of the hunting bezel shall not be less t h a n one one-thousandth of a n inch in thickness.”
