V O L U M E 27, NO. 3, M A R C H 1 9 5 5 Table 11.
Name API-103 API-104 Oil A B C D
Identification of Six Test Lubricants Tests on Base Oil Vis. Gravat 1000 oiBI F., cs V.1. 29.4 8.75 60 29.4 8.75 60
...
31.3 31.3 31.3
...
32.3 32.3 32.3
98 98 98
Polvmer Additive 1 2 3 4 5 6
Tests on Blend Vis. Gravat ity 100” 0 APT F., cs v.1. 28.0 33.1 168 28.9 33.3 172 30.3 43.1 121 31.1 52.3 144 59.8 127 31.2 31.3 60.0 127
Table I1 identifies these oils by gravity, viscosity a t 100’ F., and viscosity index of both the base and finished oils. SUMMARY AND DISCUSSION
h high rate of shear rotational viscometer has been developed for studying the shear behavior of non-Newtonian materials. Temperature effects due to high rates of shear have been satisfactorily controlled by employing thin films and making equal heat paths from the film through the outer and inner working cylinders. Operation of the instrument has covered the temperature range of 100 to 200” F. and the rate of shear range of 5000 to 460,000 set.? on oils comparable in viscosity range to 10 grade motor oils. D a t a are given for six mineral oil-polymer blends, two of which were investigated by Keeds ( 1 4 ) . Agreement is shown for the two investigations. The rate of shear effects (the maximum reduction in viscosity was 38%) were found to be reversible; that is, no permanent loss in viscosity resulted from prolonged and high rates of shear. The viscosityrate of shear coefficient, appears to be independent of temperature for these oils.
429 Preliminary experiments were also made with an inner cylinder having a nominal clearance of 0.00005 inch, with which it was possible to reach rates of shear u p to 1,200,000 see.-‘ The authors believe that the apparatus can be extended advantageously to a variety of investigations of non-Newtonian materials such as the study of greases, where the yield point can be determined and where the viscosity can be determined as a function of the “shear history.” LITERATURE CITED
Am. SOC.Testing Materials, Philadelphia, Pa., “ASTM Standards on Petroleum Products and Lubricants,” Standard Method of Test for Viscosity by Means of the Saybolt Viscosimeter, ASTM Designation D 88-44. Ibid., Tentative Method o f Test for Kinematic Viscosity, ASTM Designation D 445-46T. Bleininger, A. V., and Brown, G. H., Trans. Am. Ceram. SOC., 11, 596 (1909).
Blok. H.. Inoenieur (Utrecht).60. N o . 21. 58 (1948). Bradford, L-J., and‘Villforth, F: J., Jr., Trans. Am. SOC.Mech. Engrs., 63, 359 (1941). Bratt, D., and Duncan, J. E., Mech. Eng., 5 6 , 120 (1934). Hagg, A. C., J . Appl. Mechanics, 11, A-72 (1944). Hersey. M . D., “Theory of Lubrication.” .. pp. 116-18. John Wiley & Sons, New York, 1938. Kingsbury, A . , Mech. Eng., 5 5 , 685 (1933). Kingsbury, A . , Trans. Am. SOC.Mech. Engrs., 24, 143 (1903). Kyropoulos, S., Forsch. Gebiete Ingenieurw., 3, 287 (1932). MacMichael. R. F., J. Znd. Eng Chem., 7 , 961 (1915). Nahme, R . , Ing. Arch., 11, 191 (1940). Needs, S. J., Am. SOC.Testing Materials, Spec. Tech. Pub. 111 ,
I
(1951).
Ward, A. F. H., Neale, S. M., and Bilton, N. F.. Brit. J . A p p l . Sci., Suppl. 1, 12 (1951). RECEIVED for review March 25, 1952. Accepted December 2, 1954. Presented a t the annual meeting of the Society of Rheology, Chicago, October 1951.
Analyzer-Recorder for Measuring Hydrogen Sulfide in Air E. B. OFFUTT’ and L. V. SORG Research Department, Standard Oil Co. (Indiana), Sugar Creek, Mo.
An instrument for measuring and recording hydrogen sulfide in air in the concentration range of 0 to 100 p.p.m. has been developed for testing refinery atmospheres. The instrument is based upon the use of special film prepared by coating blank 16-mm. motion picture film with buffered lead acetate. The sample is pumped continuously through an exposure hood, where the hydrogen sulfide reacts with the film coating to form a stain. A light beam through the stained film falls on a photoelectric cell and generates an electric current proportional to the hydrogen sulfide concentration. This current operates a conventional electronic recording potentiometer. A warning alarm sounds automatically if the hydrogen sulfide exceeds 25 p.p.m.
H
YDROGEN sulfide alN-ays present in petroleum refining
operations causes concern because it is a deadly poison. I n concentrations over 20 p.p.m., it is considered unsafe (6). I t s obnoxious odor reveals it a t low concentrations, but the human nose soon becomes insensitive to the odor. The safety-mindedness of the petroleum industry demands t h a t such a hazard be continuously recognized. Hence, a sensitive instrumental method is needed for continuous detection and measurement of hydrogen sulfide, particularly in the range from 0 to 100 p.p.m. 1 Present address, American Thermometer Division, Robertshaw-Fulton Controls Co., St. Louis. Mo.
None of the instruments on the market monitors continuously and specifically the presence of hydrogen sulfide in this concentration range, and none has wide use. Some instruments measure hydrogen sulfide together with other gases present in refinery atmospheres ( 1 , 8). Another measures only hydrogen sulfide (6, 7 ) , but it was designed for analysis of gaseous streams low in oxygen content and is not continuously recording. The American Iron and Steel Institute sampler intermittently detects hydrogen sulfide by staining of lead acetate impregnated on a filter-paper tape ( 4 ) . Laboratory determination of light transmittance is required. Most refiners have had to rely on spot checks made with a hydrogen sulfide detector ( 3 ) ; these provided information only for the moment a t which they were made. An instrument has been developed for continuously measuring small amounts of hydrogen sulfide in air. It can be equipped to operate an alarm, either visual or audible, should the concentration exceed a predetermined limit m-ithin the range of the instrument. The new hydrogen sulfide analyzer-recorder is based upon the reaction of hydrogen sulfide with buffered lead acetate on a transparent moving film. I n operation, the continuously moving film is moisture-conditioned and exposed to the air streams under test. Any hydrogen sulfide present stains the film coating; the stain density is proportional to the hydrogen sulfide concentration. A light beam through the stained film falls on a photoelectric cell and generates an electric current, which operates a recording potentiometer. The recorder reads directly in parts per million of hydrogen sulfide.
430
ANALYTICAL CHEMISTRY DESIGN AND OPERATION
Figure 1 shows the complete instrument contsined in an upright m e t a l c a b i n e t mounted on casters. An electronic recardinp potentiometer of 0tb io-mv. range is located a t t h e top. The anslvzer section is j u s t below t h e recorder. Valves and the two large rotameters on the panel below the analyzer cantrol the sample-carrier air stream and a moist sir stream for conditioning the film. The rotameter tube a t the center and the valves on the lower panel are used in checking the calibration. A water s?turator for the moist air streem and the sample pump are in the lower c o m p a r t ment, to which access is gained by removal of cover8 on the rear of the cabinet. Figure 2 shows the essential parts of the sample system and the analyxr section. The former consists of a blower, which coutinuously forces a large volume (50 to 60 cubic Figure 1. Hydrogen sulfide feet per minute) of the test air from the source location to the instrument. and a variablevolume sample pump which iarees rtn aliquot of the test air into the carrier air line. T h e sample pump is a specially designed constant-speed,, positive-displacement pump built of coli rosion-resistant materials. Throughput may be adjusted from zero to maximum a s required to compensate for minor variations in film sensitivity. T h e samplecarrier air streem is controlled a t B fixed flow rate for ~ I instrument I of given range. Acting a s a diluent, it carries the sample through an H-type humidifier in the analyzer chamber. Wicking, partially submerged in water, furnishes a large evaporative surface to aid humidification. The sample then-is intraduced into the exposure hood, impinging on the film through a jet. The spent sample is exhausted from the hppdby-a fan and passes from the instrument to a vent with the aid of eductor action. T h e analyzer chamber is airtight. It is held under a slight vacuum by means of the eductor in the sample line. Thus, unexposed film does not become contaminated from the are&in which the instrument is operated. Constant temperature is maintained by itn electrically controlled heater mounted on the hesvy aluminum panel to which the various parts of the analyzer
the light beam transmitted by the film, inverselg- proportional to the hvdrogen sulfide concentration, is picked up by the photoelectric cell just beneath the.film. T h e electrical resmnse from the cell is transmitted to the electronic recorder. T h e film is the type used for 16-mm. sound motion pieturefi, hut the silver is removed from the gelatin emulsion to make it comoletelv transoarent. It is meoared for the analvser in eouinmeni deskned to apply a. J/a-ikh'trace of sensitized lead ace'tkr
solution a;d a fryer ofreactant is taken ;p by the gelatin surfacc The film is dried and rolled on reels, which are rcady far installn~~
~~~
itable, an-impartah factor for use in this instrum&. Film aging a t analyzer-chamber temperatures necessitatcs wcekly changing of the film. A 50-foot reel lasts about a week. CALIBRATION
pared by transfer&
a measured portion of pure hydrogen suifide
are placed in the bomb to mix the gas when shskkn. Ssmples so prepared were found by chemical analysis to be stable for several
RE
while passing- through a b;bhler-t,ype water saturator m o u n t d on the panel. Water levels are adjusted by levelina bottles on
ured is shown in Figure 3. Unexuosed film oasses t h k u g b the
drogen sulfide impinges on the film through a flat rectanblkr compartment with the upper surface sealed hv a thin section of
A constant-intensity light source is housed in the'upper portion of the exposure hood. A lens system focuses the light beam upon the film in the area where the stain is formed. T h e intensity of
Figure 3.
Means for film-stain formation and measurement
V O L U M E 27, NO. 3, M A R C H 1 9 5 5
431
days. The bomb must be free from dust or finely divided rust becnuse such materials appear to promote decomposition of the hydrogen sulfide. I n the calibration step, standard mixtures are fed to t,he sample pump, as indicated in Figure 2. The f l o through ~ the rot,ameter is adjusted within the range of 125 to 150 ml. per minute to provide an excess over the 50 to 100 ml. per minute normally required l)y the pump. The sample is taken from the side arm of a special Pitot-tube T through which the excess of the mixture is being p:iased. Several k n o m mixtures are passed through the instrument j the recorder positions obtained from the resulting film stains determine the instrument scale. Typical floiv rates are 2000 ml. of moist air, 275 ml. of carrier ail., and 00 ml. of test sample per minute. After calibration, all tc:;ts :ire made with the same moist air and carrier air rates. The test sample rate may be varied to compensate for slight differences bet,ween rolls of film. This adjustment may be made by n single check with a standard mixture containing 25 p.p.m. of hydrogen sulfide; the throughput of the sample pump is varied until the recorder indicates 25 p.p.m. of the scale, other rates being identical with those used in t,he original calibration. Although the instrument h a s n scale limit of 100 p.p.m., i t will
TEST OFF
i
II
I
I
I
TEST ON ZEROCHECK
/ -1
I
1
CALIBRATION W E (
i 100
IO
+ /
20
30
40
PPM k S
Figure 5 .
Typical field test record
detect up to 400 p.p.m. as limited by the sensitivity of the recorder. Through control of the carrier air rate, concentrations of hydrogen sulfide a s high a s 2000 p.p.m. have been estimated. PERFORMANCE
PPM HzS
Figure 4.
Response and precision
Figure 4 is a section of a t>-pical recorder chart obtained from measurements of standard mixtures. It illustrates the precision of the instrument. In the range of 1 to about 25 p.p.m. of hydrogen sulfide in air, the instrument is sensitive t o a change of I p.p.m.; in the range of 25 to 50 p.p.m., to about 2 p.p.m.; and in the range of 50 to 100 p.p.m., to about 5 p.p.m. The speed of response of the instrument is related to the volume of the sample system and to the time required for film stain t,o form and be picked up by t,he recorder. If the change in concent,ration is from a low value to a high one, the recorder responds in 10 seconds. If the change is from high to low, t.he response is slower. With an increase in hydrogen sulfide from 0 to 400 p.p.m., the instrument I d 1 actuate the alarm set to operat,e a t 25 p.p.m. in 40 seconds. The instrument requires several minutes to level out at each new concentration. The hydrogen sulfide analyzer-recorder has been used for continuous tests in several locations about the refinery. I n a typical location, the t,est.air stream v a s brought 50 feet to the instrument from a pump room wspected of containing dangerous amounts of hydrogen sulfide. A section of the recorder chart obtained from this installation is shown in Figure 5. Hydrogen sulfide w a ~ present intermittently. At times the concentration was as high as 20 p.p.m., which is the maximum allowable concentration for prolonged exposure. The source of the gas was t,raced by a flexible hose to a valve that, leaked intermittently. The instrument has performed satisfactorily in hot, smoky, and dusty locations and is considered suitable for general plant use.
ANALYTICAL CHEMISTRY
432 Routine service consists of daily inspection of instrument operation and addition of water to the saturator and humidifier; weekly changing of the film and inspection of the sample pump; and monthly changing of the recorder chart and lubrication of certain parts. Servicing the recorder normally requires an additional 15 minutes daily, an extra hour once a week, and an extra 2 hours once a month. LITERATURE CITED
(1) Consolidated Engineering Corp., Pasadena, Calif., “Consolidated’s Titrilog,” Bull. CEC 1810D (1953).
(2) Davis Emergency Equipment Co., Inc., Newark, S . J., “Recording Electro Conductivity Analyzer,” Bull. 11-70 (1953), (3) Forbes, J. J., and Grove, G. W., U. S. Bur. Mines, Miner’s Circ., 33 (1938). (4) Hemeon, W. C. L., Sensenbaugh, J. D., and Haines, G. F., Jr., Instruments, 26, 566 (1953). ( 5 ) Rubicon Co., Philadelphia, Pa., “Recording Automatic Hydrogen Sulfide Analyzer,” Bull. 480 (1947). (6) Sayers, U. S. Bur. Mines, Rept. Invest. 2491 (1923). (7) Schaeffer, W. H., Electronics, 22, 85-7 (1949). RECEIVED for review May 26, 1954. Accepted October 6, 1954.
Spot Reaction for Acidic Polynitro Compounds FRITZ FEIGL and VICENTE GENTIL Ministerio d a Agricultura, Rio d e Janeiro, Brazil
Translated by Ralph
E. Oesper, University of Cincinnati, Cincinnati, Ohio
When enolizable nitro compounds react with rhodamine B, they give red-violet salts, whose red solutions in benzene fluoresce orange. This finding has been made the basis of a new, fairly sensitive spot reaction for the detection of enolizable polynitro compounds.
E
EGRIWE (1) discovered that the violet precipitates formed in strong hydrochloric acid solution by the amphoteric water-soluble dye rhodamine B with antimony(V), gold( 111), and thallium(II1) ions can be made the basis of sensitive tests for these metals. According to Kuznetsov (?’), these reactions involve the production of salts of the dye, or its quinoidal zwitter ions, with the complex [SbCls]-, [AuC14]-, or [Ticla]- ions. The production of the antimony compound, whose formation may also be used for quantitative microdeterminations (8, 9, 11), can be represented as:
neutral or mineral acid solutions of rhodamine B, violet precipitates appear in many cases. These products are soluble in benzene and the resulting red solutions display an intense orange-red fluorescence in ultraviolet light. The color and the fluorescence reaction can be observed a t dilutions that are too slight to produce a visible precipitate. This behavior, which is completely analogous to that of complex metal halogen acids, is a strong indication that the reaction involves the formation of benzene-soluble salts of rhodamine B with the aci- form of the nitro compounds. When other acid groups are absent, the acidic character of organic nitro compounds is due to the formation of the socalled nitroxy acids (6)-in other words, to the enolization of the NO2 to the NO2H group. I n the case of aliphatic primary and secondary nitro compounds, there is an equilibrium between the tautomeric forms: --CHZ-XOz
n
S --CH=NOnH
CH-NO**
C=NO2H
In the case of aromatic nitro compounds, the acidification results from the rearrangement into quinoidal compounds with development of N02H groups. For example, the following equilibria are established in the case of p-nitrophenol and hexanitrodiphenylamine, respectively:
nCOO-' I
NO2
&() NO1
Analogous reaction schemes apply for the other two metal chloride ions and likewise for [SbIdI- ( 4 ) . Most of the waterinsoluble salts of rhodamine B with metal-halogen acids dissolve in benzene (toluene) to give red-violet solutions ( 5 ) , a finding that was first reported by Webster and Fairhall ( I O ) in the case of the antimony salt. The benzene solutions of most of the rhodamine salts exhibit an orange-red fluorescence in ultraviolet light. The behavior of rhodamine B toward organic acidic compounds with respect to the production of colored benzene-soluble salts has been studied in the present investigation. Enolizable nitro compounds are outstanding in this regard. When not too dilute solutions of such compounds are allowed to react with aqueous
NO2
e
,,0-NH+2
N0z
NO2
dO,H
02N&$NbXOzH NO1
N0z
Enolizable aliphatic and aromatic nitro compounds give yellow solutions in caustic alkali because formation of the water-soluble alkali salt removes the aci- form from the equilibrium. This removal resulting from salt formation with rhodamine B can also occur in the absence of water. This is proved by the fact. that the colorless solution of rhodamine B in benzene (toluene), which contains the lacto- form of the dyestuff, immediately turns red on the addition of nitro compounds which are able to produce nitroxy acids on enolization. This salt formation, beginning with the lacto- form, can be represented schematically as:
