Transmission measurements with the Beckman quartz spectrophotometer

Abstract

The Beekman quartz photoeleetri c sp ectroph otcmeter , covering th e wavelength ra nge from a bout 200 to 1,200 m illi microns, is proving of great utility in swctral t ransm ission and absorption m e asurem en ts. Esse n! ia l features of the instrument are described, including a constant-temperature enc losu re (for samples) designed a nd con structed at the Bureau. Varioll s instrumental characteri stics a re noted an d possible errors di scllssed , particularl y those that may be p re ent in the m eas urement of p olarizi ng samp les. Wavelength calibrations a re shown for two i nstruments. A de tailed ove r-all chec k of t he re li ability of data obtai ned on t he Beckman spect rop hotome ter by m eans of g las stand a rds of spectral transmittance shows it to giv e res ults ove r th e wavele ngth r a nge from 390 to 750 millimicrons fu ll y as reli able a s those obtain ed with othe r spectrophotom et ers, if indi cated precauti ons are taken.

An Alkaline Solution of Potassium Chromate as a Transmittancy Standard in the Ultraviolet*

“…Transmission measurements with* a modification of this instrument, which has a constant-temperature enclosure 7 designed and constructed at the National Bureau of Standards, have been described in detail in a paper by Gibson and Balcom [20]. All measurements on the Beckman spectrophotometer were made with a 1.000-cm cell.…”

“…the internal screw that rotated the collimating mirror. After such check or adjustment, the precise wavelength correction was then applied at each wavelength setting in accordance with the curve illustrated in figure 6 of reference [20].…”

Acid-base reactions in organic solvents. Behavior of some halogenated derivatives of phenolsulfonephthalein with different classes of organic bases in benzene

“…In the work of previous investigat ors, apparently the only organic bases employed wer e secondary aliphatic amines, which produced a blue color, as was to be expected by analogy with aqueous solutions [18,19]. 3 We discovered that the color produced in inert solven ts such as benzene and chlorobenzene dep ends on the ch emical type to which the base belongs. In short the r eactions of organic bases of various 2 E lizabeth E. M u rray, formerl y of t h is B ureau, observed th at several new volumetric flasks, said to have been cleaned with ao acid m ixture, acq u ired b lue spots on t he inner surface after bei ng filled with a benzene solution of bromophenol blue.…”

“…The spec tropho tom etric data were ob tained wi th a Beckman quar tz photoelec tric spectrophotometer [2,3] in which a pair of stopper ed cells and a spec ially design ed cell compartment were sub-stituted for the cells and cell holder supplied with the commercial instrument. Each cell consisted of a pair of optically matched crystalline quartz endplates 2 mm in thickness and a st,oppered quartz cylinder 3.8 cm in diameter and 1 em in length, open and polished at the ends .…”

“…However, the solutions can (1) C hl orophenol blue; (2) bro mophenol blue; (3) iodopbenol blue; (4) tetrabroll1o phenolpb tha lein ; (5) bromophthalein m agenta E. be considered as very nearly equivalent in concentration. Curves 1 to 4 in figure 3 are for chlorophenol blue, bromophenol blue, iodophenol blue, and tetrabromophenolph thalein, respectively. Curve 5 is for bromophthalein magenta (tetrabromophenolphthalein ethyl ester).…”