I.VDUSTRIAL i l S D ENGINEERISG C H E X I S T R Y
January 15, 1930 RUN
T a b l e I-Experimental Data CriOa Rus
Per cent 1 2
3 4
6.20 6.20 8.60 8.60 8.36 8.36 7.68 7.70
5
6
127
tested against a n alkali oxidation method, which it checked very closely, as is seen from Table 11.
CrzOa Per cenl 15.05 15.05 8.77
T a b l e 11-Comparison
of R e s u l t s b y Alkali O x i d a t i o n and P e r c h l o r i c Acid M e t h o d s CHROMIC OXIDEIIY ALKALIOXIDATION C H R O M KOXIDEBY METHOD PERCHLCIRIC METHOD Per cenl P e r cenl 15.12 15.05 l5,08 15.10 1 5 , 10 15,lO 1.510 I5 05
8.75
15.10 15.12
RCN
1 2 3 4
Comoarative Accuracv of Method The accuracy of this method was tested b y comparing it with c. P. potassium dichromate which had been dried a t 110' C. This salt is used as a primary standard in iodomet r y . for the standardization of thiosulfate solution. A 0.2-gram sample of the dichromate v a s reduced by adding to its aqueous solution 5 cc. of alcohol and 2 cc. of concentrated hydrochloric acid. The solution was evaporated to dryness o n the water bath. It was taken u p with a little Jvater and oxidized by the addition of 5 cc. of perchloric acid (60 per cent c. P.) as described above. The oxidized solution required the same amount of thiosulfate solution for its titration a. the original dichromate solution. It was also
The perchloric acid method is more accurate than the ~1~~ advantages of this method over gravimetric the alkali oxidation method are its rapidity, the comparatively easy separation of iron and alumirlum from chromium. and the purity alld stability of the oxidizing reagent. Acknowledgment This investigation chief ,,llen1ist of the indebted to hinl for
J
at the suggestion of J. Ehrlich. chemical ~ c0., ~ alld~the FT.riter ~ is~ instructive suggestions in this Tvork, -
Literature Cited (1) Treadwell and Hall, "Analytical Chemistry." 4th ed., Vol 11, p. 102.
A New Application of the Abb6 Refractometer in the Analysis of Lacquer Thinners' J. D. Jenkins PITTSBURGH PLATE GLASSCOMPANY, MILWAUKEE WIS. ,
T
HE use of the dispersion scale on an Abbe refractonie-
ter has been found to be a rapid and comparatively accurate method of determining the toluene or benzene content of lacquer thinners. While taking the dispersion on a number of common solvents and diluents it was noticed t h a t they were sharply divided into two classes by this determination-the dispersion scale reading of the aliphatic compounds, alcohols, esters, ketones, etc., areraging very close t o 41.4, while the aromatic hydrocarbons fell very near 36.6. The determinations on a number of these materials are shown in the accompanying table. A study of this table will show the extent of variation of SOLVENT E t h y l alcohol, tech. Methyl alcohol, synthetic Isopropyl alcohol, tech. Isopropyl alcohol, c. P. Pl-ormal butyl alcohol, tech. Sec-butyl alcohol, tech. Tertiary butyl alcohol, tech. Amyl alcohol, tech. Isoamyl alcohol, c. P. Acetone, tech. Methyl ethyl ketone, tech. E t h y l acetate, tech. Isopropyl acetate, tech. Isopropyl acetate, tech. Normal butyl acetate, tech. Sec-butyl acetate, tech. Pentaacetate, tech. Amyl acetate, c . P. Butyl propionate, tech.
R E F R A C T I VDISPERSION E ISDEX SCALE 25' C. READING
the dispersion reading from the mean value for aliphatic X more marked variation is evident compounds-41.4. among the aromatic compounds. The large majority of lacauer thinners in Dresent use. however. contain toluene as 1 Received September 16, 1929. Presented before t h e Division of P a i n t a n d Varnish Chemistry a t t h e 78th Meeting of t h e American Chemical Society, Minneapolis, M i n n , September 9 t o 13, 1929.
the only aromatic hydrocarbon. When homologs are used they are generally present in relatively small amounts. The presence of large proportions of higher homologs of toluene will usually be evident b y the odor or evaporation characteristics, and in this case the results of the refractometer test should be checked b y a determination of the per cent insoluble in 75 per cent (by weight) sulfuric acid. The dispersion scale reading of rnixtures \\as found to be a straight-line function of the volume composition within the limits of accuracy of the determinations. This fact permits a yery rapid and reasonably accurate determination of the content of toluene. SOLVENT Cellosolve, tech. Methyl Cellosolve, tech. Butyl Cellosolve. tech. Cellosolve acetate, tech. E t h y l lactate, synthetic Methyl oxybutyrate, tech.
DISPERSION REFRACTIVE IKDEX SCALE 250 READING 1,4073 41.4 41.5 1,4035 41.3 1,4183 41.3 1,4048 41.3 1.4116 41.4 1.4099
c.
Petroleum naphthas: Oleum spirits V. hl. & P. naphtha Toluene substitute Toluene substitute
1,4364 1.4322 1,4059 1.4133
40.7 40.8 41.1 41.4
Turpentine, gum Benzene, tech. Toluene, tech. Xylene, c. P . Xylene, tech. Solvent naphtha, tech.
1,4533 1,4955 1,4930 1,4940 1.4940 1,4846
40.0 35.4 35.6 35.9 36.0 36.5
On a mixed lacquer thinner where the hydrocarbon is toluene, it has been found that the average accuracy is about f1 per cent of toluene. This is sufficiently accurate on most work. such as the analysis of comDetitive products, because the rariation from b a t l h to batch-will be of the same order Of ma@itude' This method does not indicate the presence of petroleum
A.-l-SLYTICAL EDITI0.L-
128
hydrocarbons, as these have approximately the same dispersion scale reading as other aliphatic compounds; consequently, if petroleum hydrocarbons are present, they must be determined in some other manner. They may be distinguished from aromatic hydrocarbons by the solubility of the latter in fuming sulfuric acid; or, if the hydrocarbon
Vol. 2 , s o . 1
content of a thinner is determined by two methods: ( a ) from the dispersion scale reading, ( b ) from the per cent insoluble in 75 per cent (by weight) sulfuric acid, then a marked difference between these two determinations may be taken as indicating the presence of petroleum hydrocarbons, in amount approximately equal t o the difference.
A Blast Lamp for Natural Gas’ Harold H. S t r a i n C A R N E G I E INSTITUTION OF WASHINGTON,
DNISIONOF
vv
HEN natural gas is burned in a blast lamp difficulty is experienced in obtaining a well-defined, hot flame t h a t will not blow away from the burner. Although these difficulties have been partially overcome by the construction of blast lamps utilizing a mixture of gas and air (1, S ) , such burners do not lend themselves t o the ready
c
1 Figure 1-Blast
1
Lamp for Natural Gas
adjustment demanded by many technicians, particularly glass blowers. After experimenting with several burners, the writer de1
Received December 9, 1929.
PLANT
BIOLOGY, STANFORD
UNIVERSITY, C A L I F .
vised a blast lamp for use with natural gas which is easily adjusted and produces a very pointed, hot flame. This lamp, shown in cross section in Figure 1, makes use of the injector principle of the Bunsen burner ( 4 ) in preparing a mixture of gas and air which is then burned as in the ordinary blast lamp. The burner consists of a cylindrical tube, B , mounted on a metal block, H , which is pivoted on a metal stand, I . The burner tube, B, is provided with a sliding tip, F , and a rotating air shutter, D , similar to that of a Meker burner. The gas enters the burner through jet C in the burner tube base. The compressed air enters the burner through the curved tube G, and is emitted through jet E. Jets E and C, which mere made in several sizes, screw into place as do those in many blast lamps and Afeker burners. To operate the burner, the air shutt’er, D, is first closed. A moderate supply of gas is then turned on and lighted a t the open end of the burner tip, F . Then the air shutter is opened until a blue flame is obtained. Finally compressed air is blown through jet E, producing the typical blast lamp flame. As the composition of the air-gas mixture depends largely upon the rat’e of flow of gas through jet C (.$), the air shutter, D, needs little adjustment. Moreover, the gas-air mixture has a sufficiently high rate of flame propagation so that i t may be burned in the usual manner without danger of t’he flame “blowing off” (2). The construction of a hand torch for use with natural gas and embodying the principles here described is now in progress. L i t e r a t u r e Cited (1) Chapin, J. I N D . B N G . CHEM., ?, 46 (1915). (‘2) Glaser, Z . angeu. Chem., 36,38 (1923). (3) hfccullough, J . A m . Ckem. SOL.,37,144 (1913). (4) Pfotenhauer, C. .4., 9, 8 5 i (1915).
New Insecticide I n the great war with insects man has a new and promising weapon in the form of rotenone, a crystalline material which is both a contact and stomach poison This insecticide is especially welcomed by scientists a t this time, when they are looking for organic compounds to take the place of lead arsenate, which leaves an undesirable residue on fruit. T h e demand for organic insecticides is much greater than the supply, according to R. C. Roark, of the Bureau of Chemistry and Soils, United States Department of Agriculture. The most widely used materials in this class are nicotine and pyrethrum flowers. Nicotine is derived only from the stems and floor sweepings of tobacco. Pyrethrum flowers are grown to a limited extent in California, but practically all of the 11 million pounds used annually in this country is imported from Japan. This leaves rotenone in a field where there is little competition. This material has been obtained mostly from the roots of derris, a plant grown in the rubber plantations of Sumatra
and the AIalay Peninsula. Another promising source of rotenone is “cube,” a wild plant which grows in t h e mountains of Bolivia and Peru. On account of the limited supply of nicotine and the dependence upon Japan for pyrethrum flowers, scientists of the department are looking t o the production of insecticides of plant origin in the Cnited States. Derris and cube are both promising sources of rotenone, although cube contains nearly three times as much of the active ingredient. Careful tests have shown t h a t roots of this plant contain as much as 7 per cent rotenone. It is thought t h a t derris might be grown in t h e southern part of Florida. Cube grows a t high altitudes in Bolivia and Peru and might be suited t o the Southwestern States. Very little is known about the plant a t present. I t s correct botanical name is not even known, but its action on aphids and other insects warrants a thorough study as to the possibilities of growing the plant in this country.
