December. 1926
I N D UXTRlAL A N D ENGINEERING CHEMISTRY
sium oxide in the presence of other oxides was investigated further by comparing the promoting action on iron of each of a number of different oxides with that of the same oxide in the presence of potassium oxide. The results appear in Table 111. These results substantiate the conclusion that potassium oxide has a marked promoting action in the presence of difficultly reducible oxides of a somewhat acidic nature, such as those of manganese, tungsten, silicon, and aluminum, and show also that its addition to iron containing oxides of metals closely related to iron, such as those of nickel and cobalt,
1309
results in a lowering of the activity typical of its effect on pure iron. T a b l e 111-Comparative
No. 949 950 902 916 915 914 906 942
KtO
... ... 0.33 ... 0.57
0.30
...
0.33
Data o n Single- a n d Double-Component Promoted Catalysts NH3 AT 450' C. AND 5000 S. V. Second oxide 30 Atmos. 100 Atmos. Per cent Per cent Per cent 4.67 7.49 SiOz0.51 5.33 10.90 SiOz 0 . 7 5 W 1.71 3.51 4.83 w 0.59 10.50 4.53 7.42 Mn 0 . 5 1 4.60 Mn 0 . 9 9 8.89 3.72 Ni 1.04 5.31 3.24 4.65 2.00 Ni 0 . 3 7
Indigo and the World's Dye Trade' By Warren N. Watson and Chester H. Penning CHEWICAL DIVISION, U. S. TARIFF COMMISSION, WASHINGTON, D. C.
H E world's annual production of coal-tar dyes previous to the World War approximated $90,000,000 in value, with the quantity estimated to be 313,000,000 pounds.2 Of this total, one dye, synthetic indigo (paste), accounted for 28 per cent, or 88,000,000 pounds. Despite the introduction of many new colors in recent years (about one thousand chemically different dyes are now in commercial production), indigo, one of the oldest of dyes, has maintained its position as the leader in quantity and value, and is considered to be an index of the trend of the world's trade in dyes. I n the United States indigo has ranked first in value of all dyes made during each of the years 1919 to 1925, inclusive, and either first or second in quantity. It holds a similarly important position in each of the principal foreign dye-producing countries. It has attained this position on account of its fastness and reasonable cost. For many years indigo was the fastest blue dyd for either cotton or wool, and until recently has had no serious competitors. Synthetic indigo was first made by Adolf von Bayer in Germany in 1880 from toluene, and was almost immediately placed in commercial production by the Badische Company. Heavy financial losses were experienced in working this process, and ten years later this company purchased Heumann's patent covering a process starting from naphthalene. Production was not greatly increased, however, until 1897, when a method of increasing the yield was accidently dis-' covered. I n 1900 two other German plants began the manufacture of indigo, and Germany's exports of this dye mounted steadily, reaching a peak of nearly 74,000,000 pounds in 1913. (See Table I)
T
T a b l e I-German Exports of I n d i g o , 1880 to 1913 Year Pounds Value 1880 1,096,885 1890 1,616,265 1895 1,450990 1900 4,129,216 $2,22'8',632 1901 5 982 896 3 021,172 1902 11:649:106 4,393,956 1903 15 945 872 4,924,220 1904 193246:158 5,188,318 1905 24,614,359 6,121,598 1906 28,064,558 7,514,850 1907 36 051 824 10,134,816 1908 34:074:298 9,199,890 1909 35,507,288 9,394,336 1910 38,721,594 9 427 894 1911 47,659,043 9:955:540 1912 54 733 604 10,760,932 1913 73:529:583 12,700,746
...
...
pounds in 1913. This was the only independent production outside of Germany prior to the war, although certain branch factories of the German producers had been established in France, with a production equal to the Swiss, and a small amount was made in England under similar condition^.^ I n these branch plants only the final steps of dye preparation were carried out, utilizing intermediates produced in and imported from Germany. I n this manner the German manufacturers were enabled to meet the French and English patent requirements, keeping their trade seorets to themselves and centralizing in Germany the complex and fundamental operations involved in the preparation of intermediates. Another factor favoring the operation of branch plants in France was the French tariff, which permitted the Germans to ship dyes whose manufacture had been completed in plants operating in France to French colonies free of duty. Pre-War Consumption
The distribution by quantity and value of the German and Swiss exports in 1913 is given in Table 11, which indicates that the consumption of indigo is widely distributed. China, where blue is a national color, stands preeminent, using more than all the rest of the world together. China in 1913received nearly 65 per cent of the total exports of indigo from Germany and Switzerland. The United States, Austria-Hungary, Great Britain, Japan, and the East Indies were also important consumers during that year. T a b l e II-EXDOrtS Country France Great Britain Italy Netherlands Austria-Hungary Belgium Sweden Rusqia Denmark Spain Portugal Egypt British India, etc. China Japan East Indies, etc. United States All other Total
of I n d i a 0 f r o m G e r m a n y a n d S w i t z e r l a n d . 1913 ;FROM GERMANYFROMS W I T Z E ~ L A N D Pounds Value Pounds Value 712,968 $304,798 1,102 $ 767 21'458'563 601 208 379,102 245 639 aCG47 1i ,'931 1:347:011 202:131 18,739 3,601 3,000,020 476,089 689,599 23;,892 124,710 37,436 21,429 8,004 121,033 33,069 956,796 55,556 873,464 29,983 19,206 3,314 25,573 5,071 3,212 147,708 112,579 5,291 122,576 21,172 882 145 977,520 203,671 714,070 2:i46 298,331 394 6 405 317 47,089,374 2,845,698 493,081 1:364:044 1,810,197 84,781 143,960 347,207 2 102 086 45,194 6,742 1,004,907 7:6;9:900 71,401 476,855 496.950 2.023.381 ... 73;529;583 12,700,'746 3,950,202 754,792 ~~
...
...
The War Period
Switzerland began the manufacture of synthetic indigo in 1911, and attained an annual output of about 4,000,000 * Received October 7 , 1926.
Shortly after the beginning of the war an acute shortage of dyes arose in the dye-consuming countries. Prices reached unprecedented levels and many dyes were not available a t
2 U. S . Tariff Commission, Census of Dyes and Coal Tar Chemicals, 1911,p. 123.
2 France, MinistPre du Commerce, Rapport General sur I'Industrie Francaise, 1919,Vol. 2 , p. 205.
INDUSTRIAL AND EiVGINEERIiYG CHEMISTRY
1310
any price. The period of acute shortage in the United States was during the last ten months of 1915 and the first eight months of 1916. The price of indigo in the United States prior to the declaration of war was about 15.5 cents per pound. The spot price reached 65 cents in the latter part of 1914 and in the middle of 1916 reached the unprecedented peak figure of $2 per pound. T a b l e 111-Imports
a
of S y n t h e t i c Indigo i n t o China -VALUE--
Year Pounds 1906 9,846,400 1907 13,125,600 1908 10,662,267 1909 12,632,267 14,957,200 1910 1911 25,213,733 1912 28,250,800 1913 42,610,000 1914 33,350,267 1915 2,018 1335 23:333G 1916 1917 173,200 200,133 1918 1919 2,506,000 20,752,133 1920 21,033,061 1921 30,299,600 1922 1923 34,146,933 1924 56,160,463 1925 58,860,900 Excess of exports over imports.
Total
Per pound
$3,i42,834 2,236,218 2,472,446 3,118,850 4,936,460 5,433,iii 7,032,205 5,855,972
so:i7
1,417,500a
34,14Sa 185 872 1S4:769 1,824,084 15,980,028 11,597,659 10,210,001 9,453,534 19,208,638 12,558,344
0.21 0.20 0.21 0.20 0.19 0.16 0.18 0.70 1.46 1.07 0.92 0.73 0.91 0.55 0.34 0.28 0.34 0.21
I n this emergency not only were various substitutes used, but available stocks in all corners of the earth moved to the markets of high price levels. China, the world’s greatest consumer of indigo, proved to be a veritable reservoir. During 1915 and 1916 China’s exports exceeded her imports. (See Table 111) A few shipments from China, however, were found to consist of the original containers filled with Yangtze river mud. Production of Indigo in the United States
The exhaustion of the existing supplies of indigo and other dyes, together with the continuance of the war, clearly indicated to the consuming nations the necessity of a home dye industry as a source of supply. The United States was the first of these nations to produce indigo successfully on a commercial scale. The Dow Chemical Company in 1917 produced 274,771 pounds valued a t $1.42 per pound. E. I. du Pont de Nemours and Company produced indigo in 1918, and was followed by the National Aniline and Chemical Company later in the same year. These three firms have continued the manufacture of indigo up to the present time. The Dow Company, with a large production of bromine, has supplemented its output of indigo with a series of halogenated indigoids. T a b l e IV-Production of Indigo i n t h e U n i t e d S t a t e s , 1917-25 Number of Average price Year manufacturers Pounds Value per pound $1 142 1917 274,771 $390,136 2,724.134 0.88 3,083,888 1918 0.59 8,863,824 1919 5,233,719 18,178,231 1920 13,497,981 0.74 6,673,968 1921 3,003,186 0.43 15,850,752 0.23 1922 3,962,688 0.23 28,347,259 1923 6,519,870 0.22 19,996,703 4,399,275 1924 29,121,817 1925 4,659,491 0.16
The price trend of indigo in the United States since the date of initial production in this country is of unusual interest. As shown in Table IV, this trend has been steadily downward. I n the latter part of 1926 the price dropped to 14 cents per pound, at which figure carload lots can still be obtained. This is below the price prevailing in this country in 1913, when our entire supply was imported. It is also reported t o be lower than the present price in any other country in the world. Taking 59 cents as the purchasing power of the dollar in 1925 compared with 1913, as measured by the cost of living in average American communities according to the National
Vol. 18, No. 12
Industrial Conference Board, the present price of 14 cents is equivalent to 8.5 cents per pound on the 1913 basis. Certainly, few manufactured commodities can be found in this class. Foreign Production
I n England the Ellesmere Port Works of the German firm of Meister, Lucius, and Bruning, a t which the final stages of indigo manufacture had been carried out, were taken over during the war by British interests, and after considerable research and experimentation the manufacture of indigo was accomplished with the use of British raw materials. This plant has been expanded as a unit of the British Dyestuffs Corporation, reaching a production of 1,000,000 pounds in 1922 and approximately 4,500,000 pounds in 1924. While France made some advance in dye-inaking during the war, her progress was far less rapid than that of the United States and Great Britain. Toward the end of the war, however, rapid strides were made. The total production of dyes in France in 1919 is estimated a t 6,600,000 pounds, of which indigo comprised 21 per cent.‘ I n 1920 production increased to 16,280,000 pounds, indigo constituting 40 per cent or 6,512,000 pounds. Of the 13,000,000 pounds of dyes produced in France in 1921, 5,850,000 pounds were indigo (45 per cent). A decrease in 1923 t o 4,700,000 pounds of indigo was followed by an increase to over 10,300,000 in 1924. The Compagnie Nationale des Mati&res Colorantes is the sole producer of indigo in France. Italy has been hindered in her development of a dye industry by a lack of coal, which requires her to import supplies of essential coal-tar crudes. Progress has been made, however, particularly in the last few years, and especially in 1925. Italian production of dyes increased from 50 per cent of the country’s requirements in 1924 to 65 per cent in 1925. This year also saw the first Italian production of indigo, by the Bonelli Company, one of the three largest dye producers in the country. The extent of this production is not known. Japan, because of the importance of her textile interests, was seriously affected by the shortage of dyes when German imports were cut off a t the beginning of the war. The government encouraged the industry during the war, and it developed so rapidly that a t one time more than one hundred factories were engaged in making dyes. Large post-war imports had their effect, however, and even those plants which survived required assistance. Following the increase in the import duty to 35 per cent ad valorem and the enactment of the license import control system adopted June 7, 1924, the Japanese Diet, before its adjournment on March 31, 1925, passed an act subsidizing the Japanese dye industry to the extent of 4,000,000 yen, to be distributed over a period of six years. This amount will go principally to the two largest manufacturers, the Nippon Senryo Seiyo KabuFhiki Kaisha (Japan Dye Manufacturing Company) and the Mitsui Koyan Kabrechiki (Mitsui Mining Company) of Tokyo. Experiments are being made in the manufacture of indigo, but commercial production has not yet been attained. World Trade
Taking the maximum known production for each of the world’s nine indigo plants (three in the United States, two in Germany, one each in Switzerland, Great Britain, France, and Italy), the world’s productive capacity for indigo is calculated to be in excess of 130,000,000 pounds. The world’s average consumption of indigo is estimated a t not over 65,000,000 pounds, or about 50 per cent of the present world’s capacity. 4
Chrmte L? rnduslrte, 9, 180 (1923).
I S D U S T R I A L A N D ENGIXEERIXG C H E M I S T R Y
December, 1926
-
of Indigo i n Princinal Producing C o u n t r i e s 1913 1923 1924 1925 Country Pounds Pounds Pounds Pounds Germany 75,000,000 23,704,492 59,239,920 ..... Switzerlanda 4,000,000 9,000,000 9,000,000 5,500,000 United States ..... 28,347,259 19,996,703 29,121,817 ..... Great Britain 4,500,000b ..... ..... France 4,766,267c 10,326,3&6d 8,150,000 a Estimate, b Total production of vat dyes including indigo, 5,003,713 pounds. e L'Industrie Chimique, April, 1924. d Indigo and sulfonic derivatives. Table V-Production
I
The actual quantity of indigo exported from the various producing nations, which is a more accurate measure of international trade in this dye, is given in Table VI, which also shows the value of the indigo export'ed by those nations. Germany and the United States are shown to be the principal competitors in this field. Official statistics on exports of indigo from Germany, France, Belgium, and the Xckherlands are confusing, however, since Germany exports a considerable part of her indigo through Belgium and the Netherlands, and the exports of these nations accordingly cover the product of German manufacture. Furthermore, France, Crreat Britain, Italy, and Belgium received German Reparation indigo, which in certain cases was reexported to t'he Far East; hence the exports of these countries do not consist entirely of indigo of home manufacture. Most of the indigo entering international trade is 20 per cent paste; but because of specific duties imposed by certain nat'ions, and also of the custom of using the powder instead of the paste in dyeing, a certain amount of powder occurs in international trade, especially in shipments destined for Japan. Table VI1 contains a detail of imports of indigo into China by countries of origin. Taking exports of the Setherlands and Belgium as of German origin, it is again :Ipparent that the chief competitors in that market are Germany and the United States, followed by Switzerland. Competitive Conditions
The competitive situation on indigo is typical of all the large tonnage dyes, such as sulfur black, direct black, and direct blue. The world's capacity to produce dyes, now estimated to exceed 600,000,000 pounds annually, has nearly doubled since 1913, providing a capacity in excess of normal requirements whic,h has resulted in a world-wide era of severe competition and a lowering of price levels which cannot fail ultimately to eliminate many of the existing p1:tnts. France, Great Britain, and the United States are struggling to retain their shares of the indigo trade in China, gained during t'he World War, and are meeting with strong competition from the Germans and the Sq-iss, who formerly dominated that market. The principal weapon is pricecutting. Competition between German and American firms
1311
resulted in a 27 per cent decrease in the price of indigo in Shanghai during 1925, 25 per cent paste being quoted in December a t 16.5 cents a pound, a price but slightly greater than the lowest price in the United States. This German attack on the export trade of the new producing nations is but one of the numerou9 steps being taken by the Germans to regain their lost, markets. Following the successful example of Switzerland in the establishment of branch plants in the United States, Great Britain, France, and Italy, Germany now operates or controls similar branch factories in the United States and Italy. These enable the dye cartel t o jump tariff walls and either produce or import a dye, whichever shows the greater profit, and t o exercise an influence favorable to the interests of the German trust. The amalgamation in 1925 of six German dye firms with allied concerns into one company, known as the Interessen Gemeinschaft Teerfarben Industrie A. G., is one of the greatest consolidations in the history of German finance, and is primarily intended to increase Germany's competitive strength by a reduction in manufacturing costs through the elimination of duplication in manufacture and research, and to permit the favorable purchase and control of raw material. The outstanding feature of this amalgamation is the extension of the I. G. interests to a wide variety of chemical and allied products. These include synthetic nitrogen, synthetic methanol, and organic solvents, with experimentation on synthetic motor fuels. One of the ultimate consequences of such centralized control will be a reallocation of production whereby an individual firm mill specialize on one group of products. These new fields are of special significance, as they are the chief source of income for the cartel, and dyes, which formerly occupied the major place, are in a minor position. The consolidation of the foreign selling agencies of the amalgamated concerns is an important result of this merger. Such consolidations have already been effected in Great Britain, United States, Switzerland, Belgium, Holland, Japan, Mexico, Canada, Czechoslovakia, and Russia. These fusions are bound t,o have a far-reaching effect on the competitive strength of the Germans in each of these foreign markets. The German dye industry possesses several advantages over the industries of other countries, among which are (1) availability of raw niat'erials as compared with certain countries of minor importance, ( 2 ) lower manufacturing costs in plants built before the war and paid for by pre-war profits, (3) cumulative experience, (4) the wide diversity of products manufactured, ( 5 ) the established reputation of its products among consumers, (6) a highly developed selling organization
of Indigo f r o m Principal Producing C o u n t r i e s -1923---1924---Pounds Value Pounds Value 8,195,160 '$6,199,900 9,384,321 $3,455,329 8,716,106 2,721,102 8,744,546 2,536,770 ... 12,021.037 2,.548,023 10,764,931 2,936,512 ... . .. 64,512 28,946 2,195,648 604,335 159,834 154,338 1,967,385 1,869,328 67;820 214,508 47,311 3,688,296 854,227 235',232 ' From Chinese Official Statistics, Imports from United States into China, b hTot available. Table VI-Export8
Country Germany Switzerland United Statesa Great Britain France $&e
--1913--Pounds 73,530,014 3,950,202
Value $12,685,444 754,792
...
{
Country Germany Net herlandsa Belgiuma Switzerland Great Britain France United States Hongkong Other countries Total Reexports Total net imports Probably of German origin.
Pounds 13,634,796
Table VII-Imports 1913---. Value $2,557,003
24,$81',060
3,&6,631
...
40,000 2,358,399 1,8~0,000 82,001 42,646,256 36,267
42,609,999
...
6,156 423,393 381',801
- 13,183
$7,038,137 5,932 67,032,205
-1925---Pounds 31,897,035 5,27O,O9G (6)
1923-
___
1924-
7
Value $3,523,870 169,407 10,308 1,777,092 514,962 466,242 2,548,023 573,196 14,373 $9,597,473 143,938 $9,453,535
Pounds 8,990,175 22,469,433 770,647 6,334,242 1,913,552 3,683,108 10,764,931 1,468,ti30 137,864 56,532,587 372,124 5-3
47'8, izo 1,114,452 589,738
1,591,408 1,361,120 3,863,121
of Indigo i n t o China Pounds 10,938,239 389,066 45,600 6,239,584 1,829,062 1,461,196 12,021,037 1,579,729 31,867 34,535,380 388,532 34,146,848
Value $9,515,614 1,904,270
-
Value $3,364,858 8,479,411 216,361 1,927,316 575,253 1,175,369 2,936,512 636,133 37,863 19,349,076 140.438
$19,208,638
INDUSTRIAL -4-VDENGINEERING CHEMISTRY
1312
in all of the world markets, and (7) the unified front effected by the I. G. for meeting competition. But the favorable position of the United States, Great Britain, and France in regard to raw materials points to the future production by each of a large part of their individual requirements, with the possibility of a limited export trade. It is accordingly doubtful if Germany will ever regain her lost trade in the low-cost tonnage dyes. I n the field of the high cost and specialized dyes, however, the conditions differ greatly. Both Germany and Switzerland, by virtue of long experience, are strongly entrenched in this branch which at present is the leading source of profit in the dye trade of these two countries. A considerable number of the German and Swiss dyes are covered by patents and cannot be produced elsewhere. Also, many of the highpriced dyes are consumed in such small amounts by any individual nation that their production is unprofitable on a small scale. These dyes are nevertheless essential for the textile industry. The technical difficulties in manufacture of dyzs are great, necessitating in each case a period of long development before successful commercial production. I n this connection it is of interest to note that the progress of the United States as well as of Great Britain in the production of the anthraquinone vat dyes and the alizarins has astounded the German manufacturers and has demonstrated that practically any type of color without patent restrictions can be produced outside of Germany after sufficient technical and research effort. The prices charged for the specialties by the Germans have been notably high and, in fact, have to a large degree compensated for the loss of trade of the tonnage products, as is shown by the exports of that country. Exports of dye from Germany in 1913 were about 240,000,000 pounds, valued a nearly $52,000,000; in 1925 they were by quantity 32 per cent and by value 85 per cent of the 1913 figures. The latter figure shows the relatively small decline in the total value of exports for 1925 from that of 1913.
Vol. 18, No. 12
Protective Measures a n d Developments
The fact that dye manufacturz is regarded by the industrial nations as a key industry essential in any program of national defense has led to the adoption of a variety of protective measures for the stimulation of dye and organic chemical manufacture. These include the subsidies which have been granted by Great Britain and Japan, the license system of import control adopted by Japan, Germany, Russia, and Spain, and the higher rates of duty on imports adopted by the new producing nations, including the United States, Japan, Italy, France, and Spain. Protective measures will play an important part in the maintenance and development of the dye industries in the new producing countries within the next five to ten years, and will tend to maintain a production capacity in excess of normal world requirements. Nevertheless, competition will undoubtedly reduce the world capacity to a figure nearer the pre-war level, though allowing for an increase in consump tion due to the increase in population and in per capita consumption. One of the early signs of compromise between the stronger producers in the world-wide struggle will be the conclusion of price agreements and the partial division of markets. Affiliations are also a probability. Rumors of such arrangements have already been heard. The maintenance of research for the development of new dyes and allied products and for the improvement of existing methods of manufacture are important factors not to be overlooked by any nation striving to retain its international position in the dye trade. Marked advantages will result to those firms able to produce new dyes of exceptional fastness, adapted to special use, and with economy of application. I n the long run such fundamentals as (1) cost of production, (2) availability of raw materials, (3) labor efficiency, (4) efficiency of selling organization, (5) sufficient capital without excessive capitalization, and (6) the maintenance of technical staffs with ability to give prompt and efficient technical service to consumers, will become decisive factors in determining what countries will survive this competitive era.
Detection of Alcohol Adulterants’ By J e r r y M. Haley CROMPTON & KNOWLES LOOM WORKS,WORCESTER, MASS.
ANY of the methods employed in the detection of alcohol adulterants, although of proved value, are long, cumbersome, and erratic. The present universal interest in alcohol and its denaturants appears to warrant a set of determinations which may be used with rapidity, simplicity, and dependability. Hence, a literature research was undertaken as a basis of experimentation and comparison and those tests which met the above qualifications favorably were considered as adaptable. A complete test for six of the more common adulterants can be made in one hour.
M
Test M e t h o d s METHANOL~-TO 5 cc. of a 5 per cent ethyl alcohol solution add 2 cc. of a solution containing 3 grams of potassium permanganate and 15 cc. of 85 per cent phosphoric acid per 100 cc. Allow to stand 10 minutes. Add 2 cc. of a solution containing 5 grams of oxalic acid dissolved in 100 cc. of 1: 1 sulfuric acid. When clear add 5 cc. of a modified Schiff’s reagent. The characteristic blue develops in 10 minutes. Modified Schif’s Reagent. Dissolve 0.2 gram of Kahlbaum’s 1
*
Received May 22, 1926. Georgia and Morales, THIS J O U R N A L , 18, 304 (1926).
rosaniline hydrochloride in 120 cc. of hot water. Cool and add 2 grams of anhydrous sodium sulfite dissolved in 20 cc. of water, followed by 2 cc. of concentrated hydrochloric acid. Dilute to 200 cc. and store in glass-stoppered amber bottle. AcEToivE3-Add 1 cc. of ammonium mixture (30 grams of ammonium sulfate plus 10 cc. of concentrated ammonium hydroxide in 45 cc. of water) to 0.5 cc. of the ethyl alcohol solution. Add 2 or 3 drops of a 25 per cent sodium nitroprusside solution. A permanganate red color develops. A rose-red indicates less and a blue-red a higher concentration. BENZENEeA&fix 5 cc. of alcohol with 5 cc. of equal volumes of 3 per cent hydrogen peroxide and 4 per cent sodium nitrite. Add 1 to 2 cc. of 2 N sulfuric acid. Shake and boil for 2 minutes. Cool. Add 5 drops of concentrated sodium hydroxide to 2 cc. An orange-red color denotes benzene. ALKALOIDS~-TO 3 cc. of the alcohol add a few drops of concentrated sulfuric acid. Cool and add a few drops of the following : Alkaloid Reagent. Mix 3 grams of phosphomolybdic acid with 3 grams of ammonium vanadate dissolved in 100 cc. of concentrated sulfuric acid. A color varying from violet t o orange results. 8
4 6
Hasse, C. d.,16, 999 (1921). Trifonow, I d . , 17, 700 (1923). Parri, I b i d . , 19, 2942 (1924).
