836
T H E J O U R N A L O F I N D U S T R I A L A N D Eh’GINEERING C H E M I S T R Y
narrowing a t the tip or a constriction anywhere in t h e tube. (Noticed in t h e spiral type where t h e spiral is fused on t o t h e inner tube.) These conditions t e n d t o cause choking and when this occurs the loss is always disproportionately great. TT-The length of the condenser is a factor in its efficiency (especially in t h e case of the Liebig) for lowboiling liquids. I n t h e case of t h e other forms t h e length of t h e jacket has less influence t h a n seems t o be commonly supposed. VI-In experiments where a long condenser can be conveniently used, the Liebig seems t o be preferable because it is a much less costly condenser and can be easily cleaned. Where a short condenser is required, the Friedrichs seems best. I‘II-The short Liebig or Allihn can be used t o advantage only when t h e rate of condensation is not greater t h a n from 2 t o 3 drops per second, or when some means is used, such as a glass wool plug in t h e top of t h e condenser or a test t u b e inverted over t h e t o p of t h e condenser t o prevent too rapid a carrying away of t h e vapor b y air currents. DZPARTMBNT OF CHEXISTRY UNIVBRSITY OF MISSOURI,COLUMBIA
CHAIN SCREEN DOORS BY HEXRYH
q’II4GAND
Received June 14, 1916
lTThenever t h e ordinary door of a n oven or furnace is opened a stream of intensely heated gases pours out of t h e upper part of t h e opening, while a t t h e bottom a n equivalent volume of cold air rushes into t h e furnace, chilling contents and walls, entailing damage thereto and loss of heat. Time is also lost, as t h e interior must again be raised t o the requisite temperature. Many makeshifts have been devised t o avoid t h e adverse conditions arising from t h e opened furnace door, b u t until t h e advent of t h e ingenious Wiegand chain screen door, nothing properly served the purpose. What was demanded was a door or shield t h a t would permit a clear, unhampered view of the interior of t h e furnace or o r e n ; would not in any way interfere with t h e free manipulation of t h e tools required t o care €or t h e interior; yet a door t h a t would keep t h e heat in and the cold air out; in other words, a door which should possess a t t h e same time t h e qualities of opaqueness, transparency and penetrability. This was a seeming impossibility until t h e chain door was devised b y a Baltimore inventor. These chain screen doors, in the form used mostly around metal, glass and chemical furnaces, consist of a multitude of freely hanging individual strands of steel chain suspended close together from a bar in a manner t o form a continuous sheet or curtain of chain, not unlike t h e familiar Japanese screen. This curtain of chain, hung before the uncovered opening t o a furnace and looking like a coat of mail, effectively hinders t h e heat, glare, gases and sparks from leaving t h e furnace and checks t h e entrance of cold air. The loosely hanging strands of light chain are parted with ease and pressed aside by t h e tools or other objects projected
Vol. 8, No. 9
into t h e furnace, only t o fall together again when entrance has been effected. The interstices in the links of chain permit a n unhampered view of t h e interior-in fact a better survey may be obtained t h a n under ordinary conditions, as the glare is toned down and t h e effect is similar t o looking into a furnace through a piece of wire gauze. This is particularly noticeable with those installed on electric furnaces. In some plants, when it is necessary t o work in front of t h e naked fire, the workmen are obliged t o stand back a great distance from their work and protect their bodies from the heat and glare with large sheet-iron shields which are supported b y one hand while t h e other manipulates the tools. This seriously handicaps the workman and. cuts his efficiency in half. I n some industries t h e men are obliged t o protect their eyes with dark goggles and their bodies and hands with extra heavy coverings. All such devices impede the men in the performance of their work. I n those plants where %he new chain screens have been employed the workman has both hands available for his work and may, with comfort, Ercely manipulate his tools while standing within n fewinches of his work. I n glass working, t h e heat of the uncovered furnace is intense. Measured on the thermometer it shows a temperature of 600 t o IOOO’, yet when one of these chain screens is placed in front of t h e opening the temperature is lowered t o such an extent t h a t the bare hand may be held without danger or discomfort within an inch or so of t h e protecting transparent screen. I n a boiler room where t h e Wiegand chain doors have been employed for about three years, experiments were made t o obtain a n idea of the effectiveness of the device in avoiding t h e losses arising from t h e frequently opened stoking door. A thermometer was fixed on a standard in t h e fire room a t a point opposite this door and I O in. therefrom. This position was chosen as being near t o the one usually taken b y the fireman when stoking or cleaning t h e fire. When t h e ordinary fire door was thrown open a n d t h e incandescent fire bed exposed, as is t h e case whenever t h e furnace is coaled or cleaned, the thermometer rose t o 400’ F. On covering t h e furnace opening with t h e auxiliary “chain door,” t h e temperature dropped t o 1 3 j o F., and the bare, unprotected hand could be held anywhere in front of the screened opening without discomfort. This drop of 26j’ on t h e application of the screen indicates t h a t a great quantity of heat lost by radiation and convection, through the ordinary uncovered furnace opening, may be saved by t h e employment of such a device. These chain screens have a great field of usefulness in connection with glass furnaces, porcelain ovens, pyrites roasters, chemical, shrapnel and annealing furnaces, and cupolas for melting iron and other metals. Their use around t h e electric furnace has added much t o the comfort of t h e operatives, when pouring. Chain screen doors are supplied in “automatic” and “non-automatic” forms. The automatic is employed
Sept., 1916
T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
mostly on boiler furnaces a n d is so constructed t h a t the opening of t h e fire door trips a catch, which permits t h e screen t o unroll from a cylinder, a n d fall in front of t h e furnace opening. When i t is desired t o close t h e fire doors again, t h e screen is rolled u p on its cylinder, which is permanently mounted above t h e furnace opening. T h e “non-automatic,” much used on ovens a n d other furnaces t h a t are not so frequently opened, is much simpler in construction. The chains forming t h e screen are suspended from a b a r a n d may be raised o u t of t h e way b y a hand chain running through a pulley overhead. When needed t h e screen is lowered into supporting brackets fixed a t t h e sides of t h e opening. I n some plants, whose furnaces are provided with vertically moving doors, t h e chain screen is permanently attached t o t h e b o t t o m of t h e ordinary vertical door. When the latter is raised t o uncover t h e entrance, t h e chain door rises a n d takes its place. E. J. CODDCOMPANY 700 S. CAROLINE STREET
BALTIMORE, MD.
EXAMINING COMMERCIAL BROMINE By ELWYNWALLER Received June 7, 1916
83 7
small quantity, a n d t h e assumption must also be made t h a t only Br and C1 are present. Friedheim a n d Meyerl suggest t h e application of Dechan’s process,P which was devised for t h e examination of brines, mineral waters, etc. It depends on t h e following: With a mixture of bromides a n d chlorides, addition of a large excess of K2Crz07 a n d positive acidification with HzS04, on boiling gives off Br b u t no C1 unless i t is allowed t o become very concentrated, when Cr02Clz may distil over. By t h e aid of a current of steam passed through t h e boiling solution, all t h e Br can be driven into t h e distillate, a n d i n t h e residual solution t h e C1 can be determined with AgN03. T o apply t h e process in t h e case of commercial Br, 0 . 5 t o I g. of t h e sample is weighed out i n a thin glass bulb, which is broken under t h e surface of N a O H solution. When all Br has been taken up, 50 cc. of a 3 per cent solution of HzOzis added, a n d t h e excess boiled out. Transfer t o a distilling flask, a d d I O g. K 2 C r 2 0 ~in crystals, a n d 20 cc. H2SO4 ( I : I b y vol.). Distil until t h e distillate gives no reaction for Br, avoiding a concentration beyond what would be equivalent t o 8 cc. concentrated H 2 S 0 4 in roo cc. of liquid. Then dilute t h e contents of t h e flask, a n d precipitate a n aliquot portion with A g N 0 3
T h e process was tried bur; proved unsatisfactory. To obtain t h e necessary reagents absolutely free from chlorides, is, at this time especially, a difficult matter. It was also found t h a t unless t h e concentration is brought t o a certain point, no Br whatever will distil over, though much still remains, consequently constant attention is necessary t o keep t h e degree of concentration in t h e flask between t h e proper limits. The results obtained were irregular a n d not concordant. Erchenbrecher3 treats 6 g. of t h e sample with 2 j cc. of N / 5 solution of K B r or NaBr, evaporates on t h e water b a t h , finally in a weighed dish, ignites gently a n d weighs. The C1 of t h e sample displaces t h e Br of t h e salt, a n d b y use of a table t h e proportion m a y be found. To weigh out precisely 6 g. or a n y other prescribed quantity of Br is a troublesome operation, so t h a t t h e use of a table would hardly seem t o be of advantage in this connection The principle involved can, however, be applied as will be seen later. Kubierschky4 applies t h e same principle by shaking Z j cc. of t h e sample i n a flask with 2 5 cc. of N K B r , settling 2nd taking t h e specific gravity of t h e supern a t a n t aqueous solution. With pure Br he states t h e specific gravity should be I . 2 2 7 , a n d he has made a table showing t h e gravities corresponding t o differe n t percentages of C1. T h e application of t h e above principle proved t o be a convenient mode of conducting t h e test. T h e The sample referred to showed sp. gr. at 5-6’ C . . . . . . . . 3.0286 method pursued was t o weigh out 6 t o 8 g. of t h e samat 2 5 O C .,.. . . . . 3 . 0 1 3 5 A sample marked C. P. from a well-known dealer at 25O C . . . . . . . . 3,1021 ple in a small stoppered flask. This was t h e n poured Titration of a known q u a n t i t y with s t a n d a r d Na2S2O3, a n d rinsed into a 3 5 0 cc. beaker containing about 70 is one method recommended b y many. T h e objec- cc. of water. The object in using so large a beaker 1 Z . aaorg. Chem., 1, 407. tion t o i t is t h a t this permits of working on only a Recently a sample of commercial bromine was brought t o t h e writer’s laboratory for examination. T h e impurities likely t o be present are not very numerous. If t h e material has been recovered from byproducts in t h e manufacture of substances from aromatic a n d other organic compounds, a material a m o u n t of organic substance may be present, e. g., Reymannl mentions finding I O per cent bromoform in one case. Ordinarily, only a small amount of grease, wax or paraffin, which has been used in sealing t h e container, is all of t h e organic impurity present. The presence of SO3 or HzS04 is possible, b u t t h e amount is usually insignificant. The presence of Br hydrates m a y perhaps occur, b u t t h a t branch of t h e subject does not seem t o have been investigated. The occurrence of C1 is naturally t h e chief impurity, both on account of t h e association i n nature, and also on account of t h e usual methods of manufacture. I n testing, some manufacturers determine t h e purity b y taking t h e specific gravity in a specially constructed apparatus, a n d b y reference t o a table (made u p , I know not how) read off what t h e y claim is t h e t r u e per cent of Br in t h e sample. Apparently i t is assumed, in .the construction of t h e table, t h a t C1 is t h e only impurity. The possible influence of other impurities would seem t o render this method a rather uncertain one, especially as t h e authorities2 are not altogether in accord, varying f r o m 2 . 9 6 6 t o 3 . 1 8 7 2 .
f
Ber., 8, 792. 2
Judging from the statements in Watts’ Dictionary, I. 676.
J . Chem. Soc.. 49, 682. Chem., 1894, 636.
a Z . angew.
’
LOC.
Cil.
