MAY, 1938
INDUSTRIAL AND ENGINEERING CHEMISTRY
.RATS. The main changes were in the liver; they consisted of a mild to moderate periportal lymphatic infiltration, some hyperemia, and an increasing number of focal necrotic areas with an increasing dosage of derris. These foci were scattered in the midzones of the hepatic lobules. The kidneys revealed moderate glomerular and intertubular hyperemia, but the degree was unrelated to derris dosage. Interpretation In all dogs the liver was mildly affected by the derris. In almost all experiments in which derris was mixed with the food, there was hyperemia of the liver, the sinuses being dilated with blood. In five of these animals the congestion was more intense and was accompanied by a tight constriction of the hepatic veins. When the drug was fed in capsules, these changes were not found, but in two of the three animals fatty changes occurred in the liver. There is not sufficient evidence on which to base an explanation for these differences, but the occasional presence of a small periportal lymphocytic infiltration might implicate the intestines as the source of the irritant. In rats the changes are to be interpreted as an absorption of a mild irritant via the portal vein, which, however, in larger doses becomes sufficiently potent to cause foci of necrosis in the liver lobules. These foci appear in the midzones of the lobules, thus resembling those cases in which infectious disease is the usual cause. The increasing size and number of foci with increasing dose of derris would seem to incriminate derris as the cause of focal necrosis in these rats, and also possibly as the cause of changes in the dogs. This evidence also strengthens the possibility that ingestion of derris was the cause of changes in the internal organs of the dogs. These observations indicate that rabbits can tolerate 30 mg. of derris per kg. of body weight daily for a period of 30 days without any deleterious effect on growth. In larger amounts (80 and 100 mg. per kg.) there is evidence that derris can exert a “cumulative” toxic effect, as shown by inhibition of growth and by death, where the daily administered dose was approximately 15 per cent of the acute fatal dose. This is more readily demonstrated in growing rats by a marked inhibition in growth as compared to normal, on diets containing above 0.0312 per cent of derris. Older and heavier rats placed on diets containing 0.125 and 0.240 per cent derris were better able to withstand the higher doses than were growing rats. However, at these high levels the diet proved fatal within 60 days as compared to approximately 30 days for young rats. It might be of interest to note that rats on 0.0312 per cent derris showed only a slight inhibition of growth and ate approximately 30 mg. of derris per kg. of body weight per day, in contrast to 8 mg. per kg. per day for growing dogs on a diet containing 0.04 per cent derris. According to these results, 0.56 to 2.1 grams of derris might be taken daily by a 70-kg. man without serious injury; 4.5 grams or about one teaspoonful per day might cause death eventually and, with this sublethal dose, there might be an undermining of the health with a predisposition to intercurrent disease, especially when considered in the light of suggestive results on young growing dogs. Roark ( 1 4 , basing his opinion upon studies made on the arsenic content of cabbage treated with lead arsenate, is of the opinion that cabbage similarly treated with derris would not contain more than 25 parts per million. It seems unlikely, therefore, that in fruits or vegetables dusted or sprayed with derris preparations, the concentration of derris could ever attain that employed in the present studies, in which amounts of from 78 to 400 parts of derris were present per million parts of diet. Also, experimental evidence (1, 9, 16)
595
indicates that exposure to the sun and atmosphere quickly causes derris to lose much of its toxicity. However, the effects of oxidation products or other compounds resulting from atmospheric exposure of derris have not been investigated.
Summary Derris administered orally to rabbits in amounts up to 30 mg. per kg. of body weight daily for a period of 30 days produced no demonstrable effects upon growth. In amounts of 60 mg. and above, a distinct “cumulative” toxic effect was observed. On two growing dogs a diet containing 0.04 per cent derris had a stunting effect as compared with litter-mate controls. Adult dogs tolerated similar amounts for periods up to 240 days without manifesting any gross changes in appearance, food consumption, or weight. Likewise, no significant alterations were observed in the blood and urine. Rats maintained on diets containing 0.0078 and 0.0156 per cent derris grew as well as the controls. Rats on 0.0312 per cent derris showed only a slight inhibition in growth; the inhibition was more pronounced as the concentration of derris was increased. On diets containing 0.125, 0.25, and 0.5 per cent derris, the animals did not live. Although the decreased growth rate might have been due partly to lowered food intake, the toxic effect of the derris in the diet should not be overlooked. Pathological studies indicated that derris in all the concentrations used was somewhat injurious to dogs and rats, the liver being the only organ consistently affected. In rats the first effect was a periportal irritation, followed by midzone focal necrosis with larger doses. In dogs the effect in the majority of cases was a periportal irritation, accompanied in most of these cases by vasoconstriction of the hepatic veins, and passive congestion. Further studies of a wider scope are needed before derris or any of its oxidation or decomposition products may be pronounced wholly innocuous when present in minute quantities on fruits or vegetables subjected to dusting or spraying with insecticides containing derris as the active ingredient.
Acknowledgment The writers wish to express their thanks to Frank L. Apperly of the Department of Pathology, Medical College of Virginia, for his cooperation in making the pathological studies here reported.
Literature Cited Ambrose and Haag, IND.ENQ.CHEM.,28,815 (1936); 29, 429 (1937). Campbell, Sullivan, and Jones, Soap, 10 (3),81, 85,87,103,105, 107 (1934). Davidson, U.S. Dept. Agr., Bull. 1228 (1924). Flippance, Gard. Bull. Straits Settlements, 2, 246 (1920). Fulmer, Ontario Dept. Agr., Bul2. 351 (1930). Hamilton J. Econ. Entomol., 26,555 (1933). Huckett, Ibid., 27,440 (1934). Huckett and Hervey, Ibid., 28, 602 (1935). Jones, Gersdorff, Gooden, Campbell, and Sullivan, Ibid., 26,451 (1933). Lapparent, Rev. Zoo2. A g r . , 30, 145 (1934). McIndoo and Sievers, U. S. Dept. Agr., Bull. 1201 (1924). McIndoo, Sievers, and Abbott, J. Agr. Research, 17,177 (1919). Roark, private communication. Roark, U. S. Dept. Agr., Misc. Publ. 120 (1932). Van der Laan, Indische Mercuur, 58, 257 (1935). Walker and Anderson, J . Econ. Entomol., 28,603 (1935). Wells, Bishopp, and Laake, Ibid., 15,90 (1922). RECEIVED December 6, 1937.
Mixed Polymerization of Butenes
by Solid Phosphoric Acid Catalyst
Polymerization of isobutene, normal butenes, and mixtures of isobutene and normal butenes under 7.8 atmospheres pressure at 95-120, 177, and 120" C., respectively, produced polymers containing 70, 55, and 74-80 per cent, respectively, of octenes which hydrogenated to octanes of 98-100, 83-85, and 95-97 octane numbers, respectively. Polymers formed from mixtures of isobutene and n-butene under 42 atmospheres pressure at 149" C. contained 88 per cent by volume of octenes which hydrogenated to octane of 95 octane number. For the production of octanes of high antiknock value, polymerizing iso- and n-butene mixtures was superior to mixing the polymers formed separately from each of these butenes. For example, octane derived from 50 per cent isobutene and 50 per cent n -butenes by mixed polymerization and hydrogenation had an average octane number 3.5 points higher than that of an octane blerid composed of 50 per cent hydrogenated di-n-butene and 50 per cent hydrogenated diisobutene (isooctane).
V. N. IPATIEFF AND R. E. SCHAAD Universal Oil Products Company, Riverside, Ill.
T
HE fact that heptenes are formed by the mixed polymerization (6) of butenes and propene suggested the possibility of producing octenes of highly branched structure by mixed polymerization of isobutene with normal butenes. According to expectations, the formation of such isoijctenes followed by hydrogenation yields octanes of high antiknock value suitable for use in production of aviation gasoline. Polymerization of butenes by the solid phosphoric acid catalyst (7, 8, 9, 17) is considered to involve the intermediate formation of esters (1,2, 6, 8,9,12, 13,18) as proposed in explanation of catalytic polymerization of olefins in the presence of acids. Ipatieff, who was the first to apply the ester hypothesis to phosphoric acid in 1935 (6), suggested that two molecules of ester interact, in contrast to the earlier view (1, 2 ) that the ester reacts with the olefin. When the molecules of ester react with one another, they may eliminate the elements of phosphoric acid in different ways, and thus produce isomeric polymers and regenerate, phosphoric acid. Thus isobutene gives tert-butyl phosphate, two molecules of which react and produce diisobutene. Similarly 1- and 2-butenes, which have been shown to isomerize into each other (11), form sec-butyl phosphate; this reacts further to form di-n-butene. From gas mixtures containing n-butene and isobutene, both s e e and tert-butyl phosphates form and interact to yield mixed or cross dimers. I n each case the resultant octenes m a y also produce esters, and these may react with either see- or tertbutyl phosphate or with themselves to give trimers or higher polymers. Polymerization of isobutene, nbutenes, and mixtures of iso- and nbutene under 7.8 atFIGURE1. EFFECT OF COMPOSITIONmospheres pressure OF BUTENEMIXTURES ON THEIR a t 95-120, 177, and RATESOF POLYMERIZATION AT 121124" C . A N D 7 . 8 A T M O S P H E R I C 1 2 0 " C., r e s p e c tively, produced PRESSURE
liquid polymers containing 70, 55, and 74-80 per cent, respectively, of octenes (boiling a t 100-120" C.) which hydrogenated to octanes of 98-100, 83-85, and 95-97 octane numbers, respectively. Under 42 atmospheres pressure at 149 O C., isobutene-n-butene mixtures yielded polymers containing 88 per cent by volume of octenes which were hydrogenated to octane of 95 octane number. Similar operation on four-carbon fractions of refinery gases gave polymers containing 85-95 per cent of octenes which, on hydrogenation, yielded octane of 96 octane number. The chemical nature of these polymers was evidenced by the same facts that Ipatieff (6) offered for propene polymersnamely, almost complete solubility in 96 per cent sulfuric acid a t 0" C., catalytic hydrogenation into paraffins, bromine numbers agreeing with those calculated for monoolefins, and carbon-hydrogen ratios corresponding to those of CnHzn. Also, application of the depolyalkylation method of Ipatieff and Pines (10) showed tert-butyl groups present in isobutene dimers and in mixed dimers of iso- and n-butenes. By this test di-n-butene appeared to contain a small proportion of 596
MAY, 1938
INDUSTRLAL AND ENGINEERING CHEMISTRY
tert-butyl groups, but this was probably due to isomerization of n-butenes into isobutene during catalytic polymerization, as observed independently in this laboratory and by others (3, 18).
Apparatus and Procedure The butenes were prepared by catalytic dehydration (5) of butyl alcohols over activated alumina at 427" C. Isobutene was formed from iso- and tert-butyl alcohols, and mixtures of 1and 2-butene were o b t a i n e d from secbutyl alcohol. For the polymerization tests the butene or butene mixture was s t o r e d in a s t e e l charger (11); placed under the desired nitrogen pressure (7.8 and 42 atmospheres) and then passed through small copper tubing t o the steel 25 50 75 tube (14 mm. inside --CpE,,cEHYDROGE/YATEDD//SrnW/Z /NM/xTuRE w/rH HYDROGENATED diameter), containD~NORMAL aunw.. ing the solid phosFIGURE2. OCTANENUMBERSOF phoric (60 cc.,acid 51.5 grams HYDROGENATED DIMERSFORMED BY of 4-10 mesh parSEPARATE AND MIXED POLYMERIZATION OF ISOBUTENE AND NORMAL BUTENES sulated, electrically
E,"da2ui:
~~~~~~
bronze block furnace provided with a thermoregulator which controlled the temperature within *20 c. Liquid polymers and unreacted butenes were released through a needle valve at the lower exit end of the nearly horizontal catalyst tube to a Pyrex receiver and gas separator from which the butene passed at a controlled rate through a calibrated flowmeter; then it was liquefied in a trap cooled by solid carbon dioxide and acetone. Both the gases charged and the combined exit and dissolved gases were analyzed by the Podbielniak low-temperature fractional distillation (15) and by sulfuric acid absorption. Sulfuric acid of 63 per cent concentration was used for determining isobutene in the Podbielniak four-carbon fraction, and then 72butene was determined on the same sample by absorption in 87 per cent sulfuric acid. By means of a Vigreux distilling column the polymers were separated into dissolved butenes, octenes, and higher boiling polymers (largely dodecenes). The octenes were hydrogenated
TABLE11.
PROPERTIES
597 O F HYDROGENATED DIISOBUTENE, AND THEIRBLENDS
DI-*BUTENE,
% hydrogenated dimer of:
Isobutene n-Butene Properties of octane or o c t m e blend: Octane No. n %o
di0 rlnalysis
100 0
75 25
50 50
75
100
98 95 92 1.3949 1.3958 1.3972 0.6972 0.7001 0.7031
87 1.3982 0.7053
83 1.3999 0.7079
Calcd. for CaHn 84.11 15.89
Found 84.08 15.94
c, %
H, %
25
0
Found 84.08 16.09
corn letely in the presence of 10 per cent by weight of Baker's blaci nickel oxide b heating for 4 to 6 hours at 200-240' C. in an electrically heated lpatieff rotat,ing autoclave (3.5-liter capacity) under 100 atmospheres initial hydrogen pressure. Completeness of hydrogenation was shown by the absence of reaction with nitrating mixture which consisted of one volume of concentrated nitric acid and two volumes of 96 per cent sulfuric acid. Octane numbers were then determined (C. F. R. motor method bymatching with isooctane blends) on the 95-121' C. fractions of the hydrogenated products.
Production of Octanes Polymerization of isobutene, followed by catalytic hydrogenation, produced octane fractions with 98-100 octane number. Similarly, n-butenes yielded octanes of 83-85 octane number, and mixtures of iso- and n-butenes gave octanes of 95 to 97 octane number. Data on conditions of operation and yields are shown in Table I. Blends of the octanes derived from separate polymerization of iso- and n-butenes followed by hydrogenation had intermediate octane numbers as shown in Table I1 and Figure 2.
Properties of Butene Polymers The Polymers Of iS0- and n-butenes and of their mixed or cross Polymers had the Physical Properties indicated in Table 111. The distillations (Figure 3) were made by the Podbielniak high-temperature method (14).
Test for tert-Butyl Groups in Butene Dimers Depolymerization tests were made On cc* each Of Octene, tert-butylbenzene, and sulfuric acid, but a t room temperature
TABLEI. POLYMERIZATION OF BUTENES AND PRODUCTION OF OCTANES Experiment No. Pressure, atm. Temperature, C. Butenes charged, g./hr./cc. catalyst Isobutene, mole % 1-Butene, mcle 2-Butene, mole % % Exit and dissolved gas, g . / hr./cc. catalyst Isobutene, mole % I-Butene mole %Butene: mole
@
Polymer: yo b y wt. of charge Co./hr./cc. catalyst CsHla content, vol. % Calcd. % of polymer derived from: Isobutene n-Butene Octane No.: Octene Octane Blending octane No. of octene (25 vol. Yo in fuel A-3 of 43.6 octane No.)
8-73
10-60
7-24
8-99
10-45
8-83
10-9
10-10
10-21
7 8 177
7 8 177
7.8 95
7 8 120
7 8 80
7.8 120
7.8 120
7 8 120
42.5 149
0.88 0.0
7";:;
0.28 8.7
0.77 1 4
$;::]
6 95 96.0 4 0
5.40 4.75 91.4 84 8 8.3 11.6
1.37 0.58 46.0 36.5 53.5 63.1
0.32 26.5 74.0
0.87 27.1 72.3
0.27
0.16 1.6 96.6
0.36 3.4 91.0
gi,'i]
0.28 0.71 0 . 7 0 0.48 6.6 56.0 58.0 64.7 90.8 36.2 39.2 32.3
0.33 8.8 84.8
72.0 0.9 55.0
64.0 0.6 59.0
0 100
81 83
88.0 10.3 70.0
87.0 6.5 72.0
91.5 5.6 71.0
74.0 1.3 76.0
54.0 0.4 80.0
49.0 0.2 74.0
58.0 0.7 88.0
90 10
58 42
64 36
48 52
42 58
84 97
96
0.2 99.8
100 0
97 3
...
85 100
98
85
... ...
...
...
98
..
.
. .,
95
.,,
95
0
PO
40
60
80
Kx)
P€FCE#T OV€R, B Y YOLUM€
136
119
..
...
FIGURE 3. HIGH-TEMPERATURE PODBIELNIAK DISTILLATION OF POLYMERS (ON GAS-FREE BASIS)
VOL. 30,NO. 5
INDUSTRIAL AND ENGlNEERING CHEMISTRY
598
Properties of Octane Fractions TABLE 111.
FracB. P. tion (746 Mm.), No. O C.
BUTENEPOLYMERS
PROPERTIES O F Val. Per Cent 4'
Bromine No. Found Calcd.
Mol
ny
Wt.'
Isobutene Polymers Formed a t 95' C. (Expt. 7-24) 0 1 2 3 45
5 6b 7 Residue
0-45 45-99 99-102 102-103 103-107 107-173 173-177 177-243
.. . ..
12.5 1.6 4.0 6.4 45.0 7.7 15.9 6.7 0.2
. ..
....
Gas
.. .. .. .
:::
1.4080 1.4104 1.4109 1.4139 1.4257 1,4330 1.4422
,
0.7190 0.7229 0.7607 0.7667 0,8023
ii6 ,
1
.. . 148 143 117 76
..
175
...
...
... .. . 143
.
. 95 ..
n-Butene Polymers Formed a t 177' C. (Expt. 8-73) 1 2 3 4 5
6 7 8 9C Residue
,
.. . .
2.4 6.1 8.5 9.5 21.9 6.9 4.1 6.6 27.0 7.0
... ...
....
0.7254 0.7350 0.7378
152 150 139 148
iia ... ... ... ...
....
0.7638 0.7653
....
iiC
143 143 143 143
...
...
120 107
168
0.7877
i4i
...
95
Polymers Formed from 46% Isobutene-54% n-Butenes a t 120' C. (Expt. 8-83) 0 1 2 3 4d 5 Residue
0-34 34-102 102-110 110-112 112-113 113-176
.....
Analysis: 14.45. b .4nalysis: 14.29. 0 Analysis: H , 14.23. d Analysis: 14.24.
0.4 8.0 14.0 8.0 48.0 16.0
,
. ..
1.4121 1.4163 1.4174 1.4212 1.4336 1,4520
...,
5.6
... ...
....
Gas
0.7255 0.7291 0.7362 0,7660
...
152 154 155 157 104 83
,.. iii
...
...
... i4i
The octanes (boiling a t 95-121" C.), obtained by hydrogenating the octene fractions of the above butene polymers, were fractionally distilled by Podbielniak's high-temperature method (14). The yields of the different fractions and their physical properties are given in Table V. Fractions 2 t o 7, inclusive (boiling a t 110" C.), of the octane derived from the isobutene-n-butene mixture (Table V, experiment 8-83) were combined and refractionated through the high-temperature Podbielniak column. This redistillation effected a further separation (Table VI), apparently into 2,Zdimethylhexane and 2,2,3-trimethylpentane. Octane numbers of different fractions of these octanes obtained from mixtures of isobutene and n-butenes ranged between 94 and 99. The physical properties of the fractions listed in Table V showed that octane derived from isobutene consisted mainly of 2,2,4-trimethylpentane mixed with higher boiling octane. [Since this paper was written, results have been reported by HOOC, Smittenberg, and Visser (4) on polymerization of isobutene and normal butene separately in the presence of phosphoric acid on a carrier a t 160 and 170" C., respectively, followed by hydrogenation to produce octanes.] The octane
143 143 95
...
Calcd. for CsHie: C , 85.62; H , 14.38; found: C , 85.40; H ,
TABLEv. PROPERTIES OF OCTANE FRACTIONS (95-121' FORMED BY HYDROGENATION O F BUTENE POLYMERS
Calcd. for C12H24: C , 85.62; H , 14.38; found: C, 85.40; H ,
Fraction
No.
Calcd. for CizHza: C, 85.62; H , 14.38; found: C, 85.63; 1
2 8
Experiment No. Butene polymerized B. p. of octene tested, C . Product, 225-250' C. fraction: cc. Crystals from second recrystallization, gram M . p. after f o y t h recrystallization, C. M . p. of above with authentic p-$-tert-butylbenzene, C.
Synthetic
Is0 102
tert-BuTYL GROUPS
7-24
10-60
Is0
Normal
98-108
100-120
8-73
8-83
+
Normal Is0 normal 108-1 13 112-1 13
Val.. Per Cent
Total Val., Per Cent
dz'
n %'
Octane from Isobutene Polymers Formed a t 120' C. (Expt. 8-99)
Calcd. for CBHIG:C, 85.62; H , 14.38; found: C , 85.42; H,
TESTS FOR TABLE Iv. DEPOLYALKYLATION I N BUTENE DIMERS
B. P., O C . (Mm.)
e.)
4 5 6 7 8 9 Residue
76-98 (742) 98-99 99-99 99-100 100-100 100-102 102-102 102-104 104-106
.....
4.1 8.2 9.9 12.3 12.3 12.3 12.3 8.2 7.4 13.0
4.1 12.3 22.2 34.5 46.8 59.1 71.4 79.2 87.0 100.0
....
0.6933 0.6949 0.6946 0.6955 0,6970 0.6973 0.6997 0,7025
Octane from n-Butene Polymers Formed a t 177' C. (Expt. 8-73) 60-102 (753) 102-110 110-1 10 110-112 112-114 114-115 115-120
3.8 8.0 12.2 7.8 20.8 28.2 13.3 5.9
3.8 11.8 24.0 31.8 52.6 80.8 94.1 100.0
....
1.75
1.30
0.75
0.50
1.0
0.44
0.43
0.055
0.015
0.10
77-8
77-8
76-7
73-4
76-7
1 2 3 4 5 6 7 Residue
76-7
Octane from Mixed Polymers Formed from Iso- and n-Butene Mixturea a t 120' C. (Expt. 8-83)
77-8
77-8
76-7
76-8
1
instead of a t 0" C. as carried out by Ipatieff and Pines (IO). These workers privately suggested use of the higher temperature to effect greater depolymerization and obtain higher yields of p-di-tert-butylbenzene (melting at 78" C.). Comparative tests on triisobutene a t 0" C. and room temperature (20" C. increased to 55" C. in the mixture by the heat of reaction) gave 0.1 and 1.5 cc., respectively, of the 22E-250 O C. fraction containing the p-di-tert-butylbenzene formed. After two crystallizations from hot alcohol, the 1.5-cc. fraction yielded 0.36 gram of crystalline p-di-tertbutylbenzene. As shown in Table IV, isobutene dimer gave the same result as did synthetic diisobutene prepared from isobutene by use of cold 65 per cent sulfuric acid; mixed dimer of iso- and nbutenes formed less p-di-tert-butylbenzene than did diisobutene; di-n-butene (experiment 8-73) yielded scarcely enough material for melting point determination after it had been recrystallized the four times found necessary to ensure sharpness of melting point.
2-4 5-7 8 9 10 11 12 13a 14 15 Residue
.....
105-110 (750) 110-110 110-1 10 110-1 11 111-112 112-1 12 112-112 112-113 113-113 113-1 14 114-1 14
.....
3.4 25.5 25.4 3.7 3.7 6.8 6.8 2.7 6.8 4.7 5.9 4.7
3.4 28.9 54.3
;::I
68.5 75.3 78.0 84.8
:I
100.0
0.7039 0.7054 0.7073 0.7096 0.7109 0.7137
....
....
1.3989 1.3994 1.4001 1.4009
.... ....
1.4020 1.4025
....
1.4038 1.4073
0.7071 0.7082 0.7123 0.7139 0.7158 0,7181
4 Analysis: Found: C , 84.07%; H 1 5 9 2 % . mol. wt. 114 (cryoscopic in CaHa). Calcd. for CsHia: C, 84.11 ; H, 15.89; 'mol. wt. 114.
OF OCTANE TABLE VI. REDISTILLATION OF 110" e. FRACTION DERIVED FROM POLYMER OF ISO- AND 72-BUTENES Fraction
No.
Residue
B. P. (748 Val. Total Vol. Mm.), O C. Per Cent Per Cent 8 8 10 18 30 12 40 10 53 13 9 62 10 72 85 13 113-114 9 94 6 100
.....
dz'
....
0.7026 0.7049 0.7064 0.7082 0.7103 0.7114 0.7129 0.7149
....
n %' 1.3937 1.3961 1,3976 1.3985 1.3994 1.4001 1.4017 1.4029 1.4038 1.4046
MAY, 1938
INDUSTRIAL AND ENGINEERING- CHEMISTRY
produced from n-butene polymer had a complicated composition in that the lower boiling part seemed to be a mixture of 2,4- and 2,5-dimethylhexane, whereas the higher boiling fractions apparently contained 2-methylheptane and 3,4dimethylhexane. The octane fractions produced from the mixtures of isobutene and n-butenes had physical properties indicative of 2,Zdimethylhexane and 2,2,3-trimethylpentane.
Acknowledgment The authors are indebted to R. W. Moehl for the combustion analyses, density and molecular weight determinations.
Literature Cited (1) Berthelot, “Synthkse chimique,” p. 79, Paris, 1876. (2) Butlerow, Ann., 189, 46-83 (1877) ; J . R u s s . Phys.-Chem. SOC., 1877. 38.
(3) Frost, Rudkovskii, and Serebryakova, Compt. rend. m a d . E& U.R. S. S., [N. S.]4, 373-6 (1936) (in English). (4) Hooc, Smittenberg, and Visser, 2nd World Petroleum Congr., Paris, June, 1937, Preprint. (5) Ipatieff, Ber., 36, 1990 (1903); Pines, J . Am. Chem. SOC.,55, 3892 (1933); Corson, IND.ENQ. CHEM., Anal. Ed., 6, 297 (1934). (6) Ipatieff, IND.ENQ. CHEM.,27, 1067 (1935); “Catalytic Reactions a t High Pressures and Temperatures,” pp. 622, 633, New York, MacMillan Co., 1936.
599
Ipatieff, U. S. Patents 1,993,512-13 (March 5, 1935) ; 2,018,065-6 (Oct. 22, 1935); 2,020,649 (Nov. 12, 1935); 2,057,433 (Oct. 13, 1936) ; 2,060,871 (Nov. 17, 1936). Ipatieff, Corson, and Egloff, IND. ENQ.CHEM.,27, 1077 (1935). Ipatieff and Egloff, Oil Cas J., 33, No. 52, 31-2, 99 (1935); Natl. Petroleum News, 27, No. 20, 24G-24M (1935); Egloff, Zbid., 27, NO.47, 25-6,28, 30-1 (1935). Ipatieff and Pines, J . Am. Chem. Soc., 58, 1056 (1936); S. Ovg. Chem., 1, 476 (1936). Ipatieff, Pines, and Schaad, 3. Am. Chem. Soc., 56, 2696 (1934). Kondakow, J . prukt. Chem., 54,442 (1896) ; Holleman, Walker, and Mott, “Textbook of Organic Chemistry,” 1st ed., p. 143, 1903; 5th ed., p. 150, 1920, New York, John Wiley &Sons; Brooks, “Non-Benzenoid Hydrocarbons,” p. 210, New York, Chemical Catalog Co., 1922. Morrell, IND. ENQ.CREM.,19,794 (1927). Podbielniak, IND. ENQ.CHEM.,Anal. Ed., 5, 119, 135 (1933). Zbid., 5, 172 (1933). Serebryakova and Frost, J . Gen. Chem. (U. S.S.R.), 7, 122-30 (1937). Universal Oil Products Co., British Patents 437,188 (Oct. 14, 1935), 463,272 (March 25, 1937), 463,884 (April 7, 1937), 464,671-2 (April 19, 1937); French Patent 797,584 (April 29, 1936). Whitmore, IND.ENQ. CHEM., 26, 94 (1934); Whitmore and Wrenn, J . Am. Chem. Soc., 53, 3136 (1931); Whitmore and Church, Zbid., 54, 3710 (1932). RECFOIVED November 11, 1937. Processes baaed upon the work described here are covered by pending patents.
ccNONTOXIC”SELENIFEROUS SOILS Widespread occurrence of selenium in soils has been reported (3). The presence of selenium in plants grown on these soils gives rise to a problem of both agricultural and industrial importance in that both animal and human food products are made toxic. I n view of this, extensive investigations have been carried on in the Department of Agriculture and in numerous universities and other institutions. I n all of this work it has been tacitly assumed that the presence of any considerable amount of selenium in the soil is tantamount to injury to the normal function of the soil. This paper presents a phase of the larger question of the agricultural significance of selenium in soils. I t is shown that areas exist where highly seleniferous soils do not produce toxic vegetation and that the implied assumption in previous work is unwarranted.
A
LACK of quantitative correlation between the selenium content of the soil and the vegetation has been evident throughout the entire investigation of seleniferous areas (1, 2, 3 ) . In the course of the investigations many factors influencing this lack of correlation have been unearthed. These factors may be divided roughly into the plant influences and the soil influences. This lack of correlation is certainly due in part to the variation in the forms of selenium in the soil (8) and to the distribution of the selenium throughout the soil profile, as well as to the character of the
H. W. LAKIN, K. T. WILLIAMS, A N D H. G. BYERS Soil Chemistry and Physics Research Division, Bureau of Chemistry and Soils, Washington, D. C.
soil ( 2 ) . Concurrent with these soil factors are plant factors, such as the selective absorption of selenium by some plants, its moderate absorption by others, and the limited tolerance of selenium by a third group (6). The depth a t which a plant feeds and the distribution of its root system are also items to consider as affecting the resultant absorption. Nevertheless, when highly seleniferous soils were found in Hawaii (S), it was confidently expected that toxic vegetation would be found growing on them in spite of the apparent absence of known selenium-loving plants. However, with sixteen vegetation samples which were secured, the selenium content varied from none to a maximum of 3 parts per million in the air-dry weight of the tops. Ten of these plants were unidentified. The other six consisted of four different genera, including Compositae and legumes which are frequently seleniferous when grown on selenium-bearing soils ( 5 ) . These consistently low selenium values in plants from seleniferous Hawaiian soils led P. L. Gile of this division to grow millet, a moderate selenium absorber, on a soil from the Wahiawa Erosion Experiment Station, Island of Oahu, Hawaii. Although the soil contained 12 p. p. m. of selenium, no selenium was found in the millet. At the same time, millet grown on Wabash silt loam to which had been added only 2 p. p. m. of selenium as sodium selenate had 1300 p. p. m. Hawaii was the first area where the vegetation examined from highly seleniferous soils was consistently low in selenium content. An opportunity to study the vegetation of Hawaii in detail was not offered so that the existence of a large area of “nontoxic” seleniferous soils in Hawaii is not adequately proved.
