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The osmium lamps
June, 19o5.]
2Votes a n d C o m m e n t s . THE
OSMIUM
46I
LAMPS.
The " A u e r Os," as it is called, from its inventor, H e r r A u e r von Welsbach (who also invented the m a n t l e of t h o r i u m and cerium), is constructed o[ a filament of metallic osmium. This is a rare element, the first of the heavy-platinoid group, including osmium, iridium and platinum. O s m i u m as a metal has had, till recently, but little use. except in such restricted ways as the osm-iridium point for gold pens. Of its chemical compounds, the only one t h a t is fairly c o m m o n is the t e t r o x i d e ("4-oxide") OsO,, or " o s m i c acid." as it was p,opularly but inaccurately called; this is used in s t a i n i n g thin sections of organic tissue in microscope work. Some peculiarities of this oxide are, t h a t it is readly formed by h e a t i n g the metal, t h a t it is volatile~ and worst of all t h a t it has occasioned bad accidents to eyesight. T h e v a p o r of this t e t r o x i d e on t o u c h i n g the cornea of the eye of the careless e x p e r i m e n t e r is reduced to metallic osmium, which forms an artificial but u n r e m o v a b l e "cataract," resulting in a p e r m a n e n t clouding of the sight. ,Oll the whole, however, the metal peacefully reposed in the cabinet of chemical curiosities, till it was called upon to furnish a luciferous filament in competition with the o r d i n a r y incandescent c a r b o n lamp. A t 37 volts, and 1.5 watts per c.p., the filament is 28o mm. l o n g and has a d i a m e t e r of o.o87 mm.; it thus appears that a pound of o s m i u m can furnish m a n y t h o u s a n d lamps. T h e difficulty of m a k i n g a thin and even t h r e a d was o v e r c o m e by m i x i n g the finely-divided m e t a l with thick paste of some sticky o r g a n i c c o m p o u n d ; this was forced t h r o u g h a die made of d i a m o n d or sapphire, e m e r g i n g as a filament, which was them c h a r r e d in the steamy r e d u c i n g a t m o s p h e r e . Osm i u m is brittle when cold, but soft when heated. T h e life of the lamp has frequently extended b e y o n d 5,ooo hours. T h e rival in metallic-filament lamps is t h a t made of tantalum, but b o t h are in the state of p r o m i s i n g exp e r i m e n t a t i o n . Fritz Blau recently read an authoritative p a p e r on this subject before the E l e k t r o - T e c h n i s c h e V e r e i n of Berlin.--Eng. and Mining
Journal.
THE
TANTALUM
LAMP.
A life test of t a n t a l u m lamps, which has now p r o g r e s s e d a b o u t 55o hours, has given results that b e a r out quite fully the s t a t e m e n t s c o n c e r n i n g the lamp made by two engineers on the staff of the Siemens & Halske Company. Two lamps with clear globes have been b u r n i n g a b o u t 550 hours, and they have not fallen off in candle power as yet by IO per cent. The efficiency is a b o u t 1.8 watts per cp. for the clear globe lamp and 2 watts for the frosted globe lamp. T h e filaments get beady in appearance after a b o u t 50 hours, but c h a n g e very slowly subsequently. B u r n e d in a nearly horizontal position they sag considerably d u r i n g the first period of their life and then begin to t i g h t e n up again. T h e light has almost exactly the s a m e hue as t h a t of the N e r n s t lamp. In this test the t a n t a l u m lamps have held up better in candle power t h a n an E d i s o n lamp b u r n e d and tested with t h e m for a check.--Elec. World.
2Votes a n d C o m m e n t s . THE
OSMIUM
46I
LAMPS.
The " A u e r Os," as it is called, from its inventor, H e r r A u e r von Welsbach (who also invented the m a n t l e of t h o r i u m and cerium), is constructed o[ a filament of metallic osmium. This is a rare element, the first of the heavy-platinoid group, including osmium, iridium and platinum. O s m i u m as a metal has had, till recently, but little use. except in such restricted ways as the osm-iridium point for gold pens. Of its chemical compounds, the only one t h a t is fairly c o m m o n is the t e t r o x i d e ("4-oxide") OsO,, or " o s m i c acid." as it was p,opularly but inaccurately called; this is used in s t a i n i n g thin sections of organic tissue in microscope work. Some peculiarities of this oxide are, t h a t it is readly formed by h e a t i n g the metal, t h a t it is volatile~ and worst of all t h a t it has occasioned bad accidents to eyesight. T h e v a p o r of this t e t r o x i d e on t o u c h i n g the cornea of the eye of the careless e x p e r i m e n t e r is reduced to metallic osmium, which forms an artificial but u n r e m o v a b l e "cataract," resulting in a p e r m a n e n t clouding of the sight. ,Oll the whole, however, the metal peacefully reposed in the cabinet of chemical curiosities, till it was called upon to furnish a luciferous filament in competition with the o r d i n a r y incandescent c a r b o n lamp. A t 37 volts, and 1.5 watts per c.p., the filament is 28o mm. l o n g and has a d i a m e t e r of o.o87 mm.; it thus appears that a pound of o s m i u m can furnish m a n y t h o u s a n d lamps. T h e difficulty of m a k i n g a thin and even t h r e a d was o v e r c o m e by m i x i n g the finely-divided m e t a l with thick paste of some sticky o r g a n i c c o m p o u n d ; this was forced t h r o u g h a die made of d i a m o n d or sapphire, e m e r g i n g as a filament, which was them c h a r r e d in the steamy r e d u c i n g a t m o s p h e r e . Osm i u m is brittle when cold, but soft when heated. T h e life of the lamp has frequently extended b e y o n d 5,ooo hours. T h e rival in metallic-filament lamps is t h a t made of tantalum, but b o t h are in the state of p r o m i s i n g exp e r i m e n t a t i o n . Fritz Blau recently read an authoritative p a p e r on this subject before the E l e k t r o - T e c h n i s c h e V e r e i n of Berlin.--Eng. and Mining
Journal.
THE
TANTALUM
LAMP.
A life test of t a n t a l u m lamps, which has now p r o g r e s s e d a b o u t 55o hours, has given results that b e a r out quite fully the s t a t e m e n t s c o n c e r n i n g the lamp made by two engineers on the staff of the Siemens & Halske Company. Two lamps with clear globes have been b u r n i n g a b o u t 550 hours, and they have not fallen off in candle power as yet by IO per cent. The efficiency is a b o u t 1.8 watts per cp. for the clear globe lamp and 2 watts for the frosted globe lamp. T h e filaments get beady in appearance after a b o u t 50 hours, but c h a n g e very slowly subsequently. B u r n e d in a nearly horizontal position they sag considerably d u r i n g the first period of their life and then begin to t i g h t e n up again. T h e light has almost exactly the s a m e hue as t h a t of the N e r n s t lamp. In this test the t a n t a l u m lamps have held up better in candle power t h a n an E d i s o n lamp b u r n e d and tested with t h e m for a check.--Elec. World.