Development DU spectrophotometer

1 development

1.1 model (prototype)
1.2 model b (prototype)
1.3 model c (prototype)
1.4 model d (limited production)
1.5 model du

development

the du developed @ national technical laboratories (later beckman instruments) under direction of arnold orville beckman, american chemist , inventor. beginning in 1940, national technical laboratories developed 3 in-house prototype models (a, b, c) , 1 limited distribution model (d) before moving full commercial production du in 1941. beckman s research team led howard cary, went on co-found applied physics corporation (later cary instruments) became 1 of beckman instruments strongest competitors. other scientists included roland hawes , kenyon george.

coleman instruments had coupled ph meter optical phototube unit examine visual spectrum (the coleman model dm). beckman had developed successful ph meter measuring acidity of solutions, company s breakthrough product. seeing potential build upon existing expertise, beckman made goal create easy-to-use integrated instrument both register , report specific wavelengths extending ultraviolet range. rather depending on development of photographic plates, or human observer s visual ability detect wavelengths in absorption spectrum, phototubes used register , report specific wavelengths detected. had potential increase instrument s accuracy , reliability speed , ease of use.

model (prototype)

the first prototype beckman spectrophotometer, model a, created @ national technologies laboratories in 1940. used tungsten light source glass fery prism monochromator. tungsten used incandescent light filaments because strong, withstood heat, , emitted steady light. types of light sources differed in range of wavelengths of light emitted. tungsten lamps useful in visible light range gave poor coverage in ultraviolet range. however, had advantage of being readily available because used automobile headlamps. external amplifier beckman ph meter , vacuum tube photocell used detect wavelengths.

model b (prototype)

optical quality quartz crystals

it realized glass dispersive prism not suitable use in ultraviolet spectrum. glass absorbed electromagnetic radiation below 400 millimicrons rather dispersing it. in model b, quartz prism substituted earlier glass.

a tangent bar mechanism used adjust monochromator. mechanism highly sensitive , required skilled operator. 2 model b prototypes made. 1 sold: in february 1941, university of california chemistry department in los angeles.

the model b prototype should distinguished later production model of spectrophotometer referred model b . production model b introduced in 1949 less-expensive, simple-to-use alternative beckman du. used glass fery prism chromator , operated in narrower range, 320 millimicrons 950 millimicrons, , 5 20 Å.

model c (prototype)

three model c instruments built, improving instrument s wavelength resolution. model b s rotary cell compartment replaced linear sample chamber. tangent bar mechanism replaced scroll drive mechanism, more precisely controlled reset quartz prism , select desired wavelength. new mechanism, results more , reliably obtained, without requiring highly skilled operator. set pattern of beckman s later quartz prism instruments. although 3 model b prototypes built, sold, 1 caltech , other 2 companies in food industry.

model d (limited production)

quartz photoelectric spectrophotometer, cary & beckman, 1941

the a, b, , c prototype models coupled external beckman ph meter optical component obtain readouts. in developing model d, beckman took direct-coupled amplifier circuit ph meter , combined optical , electronic components in single housing, making more economical.

moving prototype production of model d involved challenges. beckman approached bausch , lomb making quartz prisms spectrophotometer. when turned down opportunity, national technical laboratories designed own optical system, including both control mechanism , quartz prism. large, high optical quality quartz suitable creating prisms difficult obtain. came brazil, , in demand wartime radio oscillators. beckman had obtain wartime priority listing spectrophotometer access suitable quartz supplies.

beckman had attempted find source of reliable hydrogen lamps, seeking better sensitivity wavelengths in ultraviolet range possible tungsten. described in july 1941, beckman spectrophotomter use hot cathode hydrogen discharge tube or tungsten light source interchangeably. however, beckman still unsatisfied available hydrogen lamps. national technical laboratories designed own hydrogen lamp, anode enclosed in thin blown-glass window. december 1941, in-house design being used in production of model d.

the instrument s design required more sensitive phototube commercially available @ time. beckman able obtain small batches of experimental phototube rca first model d instruments.

the model d spectrophotometer, using experimental rca phototube, shown @ mit s summer conference on spectroscopy in july 1941. paper cary , beckman presented there published in journal of optical society of america. in it, cary , beckman compared designs modified self-collimating quartz fery prism, mirror-collimated quartz littrow prism, , various gratings. littrow prism half-prism, had mirrored face. use of tungsten light source quartz littrow prism monochromator reported minimize light scattering within instrument.

the model d first model enter actual production. small number of model d instruments sold, beginning in july 1941, before superseded du.

model du

disassembled absorption cell , photo-tube compartment, cary & beckman, 1941

when rca not meet beckman s demand experimental phototubes, national technical laboratories again had design own components in-house. developed pair of phototubes, sensitive red , blue areas of spectrum, capable of amplifying signals received. incorporation of beckman s uv-sensitive phototubes, model d became model du uv-vis spectrophotometer. designation uv-vis spectrophotometer indicates ability measure light in both visible , ultraviolet spectra.

the du first commercially viable scientific instrument measuring amount of ultraviolet light absorbed substance. had done ph meter, beckman had replaced array of complicated equipment single, easy-to-use instrument. 1 of first integrated instruments or black boxes used in modern chemical laboratories, sold $723 in 1941.

it assumed du in name combination of d model d on based, , u ultraviolet spectrum. however, has been suggested du may reference beckman s fraternity @ university of illinois, delta upsilon, members called du s.

a publication in scholarly literature compared optical quality of du cary 14 spectrophotometer, leading uv-vis spectrophotometer of time.