Infrared Analysis of Rotenone-Dihydrorotenone Mixtures H. L. CUPPLES United States D e p a r t m e n t of Agriculture, Bureau of Entomology und Plant Quarantine, Beltsville, M d . S VlELV of the conil)l~~x procdure iiivolved in tlii' c*lii~iiiical analysis of niixtures of rotenone with dihydrorotenone (Z),
an infrared procedure has been developed for carrying out this determination. If a previously calibrated cell is used, and if the mixture is kno\vn to consist entirely of these compourids, an analysis involves nothing more than the det,ermination of a $ingle value of the absorbance a t a selected wave length. The infrared spectra upon which the method is based ( 1 1 diwlose that the spectra of the two compounds are very similar o v ~ rmost of the sodium chloride prism range, and show that i~oinparativelysmall differences in absorptivity are available for quantitative analyt,ical purposes. However, it has been found 1)ossihle t o obtain moderately accurate analyses by rareful deterininntioils of the absorbance a t a wave length of 11.02 microns.
From prrliniinary calibration work it was found that, wit,li tht, particular instrumental equipment and technique, the calibration plot exhibited a slight curvature, concave toward the ask of concentration. This condition is, of course, undesirable, as the absence of a straight-line relationship greatly increases the necessary calibration work. However, it was found that a satisfactory calibration could be made by dividing thc concentration range into two parts a t the 50% point arid assuming a straightline relationship over each half of the range. Table I presents the analytical results obtained oil a series of synthetic mixtures. The accuracy of a determination is about =t2% of total sample.
'I'ahle 1 . EXI'ERIMENlAL
Tlicl irifi,;ircd spectronwtric measurements were niadc oil a c~oiiinii~i~c~i:tl single-beam, recording, rock-salt prism sprctrometer. A s the uoc*uriicayand precision of the method are determined primarily Iiy the attainable precision in measuring the optical tlcnsity, or absorb:inrc, :ill measurements have been made in thi. s ~ ~ nwaled ie cell and with reference to the cell when filled with solvent, wit,h :t rock-salt plate as a n intermediate referenw standard. The melting point,s of the samples examined, in I~orosilicnte glass capillaries, n.cre: rotenone, 163' C., tiiliydrorotcfiir,Ile, 216O The prowdurc adopted \vas to measur(' the, ;~l,.-oi~li:~~ic~ at 11.02 microns of a carbon disulfide solution containing i.OO grams pvr liter of the coiiipound or mixture being analyzed, a t a f i x d cr11 length of 0.79 mm. It is obvious that t,his reduces the requiret,o the determination of a single value oi the al).+orbancc :lnalyses are made by reading directly from H previously dct.erniined calibration c-urve the percentage roniliosition t h t cwre,q)onds to the measured absorbance.
c.
Iiifrared 4naI)sis of Sjnthetic IhLciiorieUihj drorotenone 3Iixtures
HS Synthesis _.__ Infrared Anal5sis iotenone % dihydiorotenone % Rotenone 0.0 100 0 0 18.6 81.4 17.4 40.0 60 0 40.7 65.0 3.5 0 65.8 75.0 2.5 0 75.2 89 6 90.0 10 0 100.0 0 0 99.7
rC
ACKNOWLEDGMENT
The writer is indebted to Irivin Hornstein, of this lalioratory, for prqixration of the samples and determination of their nicl ting points. L I T E R A T U R E CITED
(1) C'upyles, 1%. L., a t d Homsteiti, I r w i n , J . A m Chern. S O C . , 73,
4023-4 (1951). ( 2 ) Horristeiii, Irwiii, .l.v.ir..
(.Hmt.,
23,1330-1 (19.51).
R E C E I V Efor D review -4~1'11 4, 1939. -4ccepted -4uguet 4 , 1952.
Rapid Spectroscopic Determination of Total Water Content I34ROLU J. \lOROW I T Z AND IIERBERT Y. BKOID4 .Vutional Bureurt of Standards, Washington, D . C .
'rH1,: :!pplic:ttioii 01' it11 isotope dilution technique Iins >irltleil a satisfactory m d i o d for determining total water cotitelit of materials to within 3%. This paper presents results of prelirniirary studies Lvith knon-n hydrated crystals to demonstrate the utility of the method. The method consists of dissolving a knonn amount of the hydrated compourid to he assayed in a kiioivn quanti1,y of a mixture of deuterium oxide and hydrogen oside. The ratio of hydrogen oxide to deuterium oxide is measured in the solvent both before the l i p h a t e is added and after equilibrium has taken place betx-een water molecules coming from solvent and those initially in the hydrate. The difference in these rat,ios is due to the water content of the hvdrate which nixy be assumed to be entirely hydrogen oxide, and the values olitsined determine the water content of the hydrate. 'rhc rapidity of the method has been achieved by the of spectroscopic methods with photoelectric recording. An entire arialysis can he done in less than one-half hour. The analysis 011 a nlethod using the ~v\.:ive-]crl~tll sellaration of the emission lines of hydrogen and deuterium due to the isotopic shift ( I , 2 ) . The ratio of hydrogen to deuterium can be
deteriniried by measuring the ratio of the 116 line (4861.3 -1.)to the Dp line (4860.0 -4.) coming from a mixture of the tn-o gases in a high frequency electrodeless discharge. R a t e r vapor in the discharge dissociates into H and OH and D and OD, and the ohserved ratio of the intensity of the hydrogen to the deuterium line \vi11 be a measure of the ratio of hydrogen oxide to deuterium oxide. It is assumed that the ratio of excited hydrogen to deutei iuni is proportional to the ratio of the concentration of hydrogen oxide to deuterium oside vapor. This assumption \\-a9 verified using standard samples. APPARATUS
Intensity measurements were made with a Leeds and Korthiup rotating-grating monochromator having a 3-inch grating ruled with 12,000 lines per centimeter (3). This instrument was constructed by the research department of Leeds and Northrup Co. arid was loaned to the National Bureau of Standards on a field trial basis. Detection was with a photomultiplier, direct current anlplifierl and The was placed in a sarllple tube connected to a discharge tube, where a n electrodeless discharge was maintained i,y a ~jo-megac\rcleDower suoDlv. The vapor was pumped thr6ugh the &scharg& tubes 'at "various
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