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December, 1931
INDUSTRIAL A N D EiVGINEERING CHEMISTRY Discussion
Coloring from melts gave far greater intensities of color in the final products, especially with calcium nitrate, than was the case with materials which were colored by other methods. This was caused by greater occlusion of the dye per unit volume of material during rapid crystallization, and the especially good results with calcium nitrate may be attributed to its water of crystallization. The final products by this method did not require drying. Coloring of very soluble materials by evaporating to dryness the colored saturated solution produces well-colored crystals, owing to the occlusion of the dye. The coloring of a dry fertilizer material by thoroughly mixing with it enough concentrated dye solution to color the surfaces of the particles has the advantage that the moisture content of the original material is increased only very little. When coloring potassium chloride in solution, most satisfactory results were obtained with very soluble dyes. Less soluble dyes were either salted out or reacted to form a precipitate. Poor distribution of color resulted with monoammonium phosphate when basic dyes were employed, owing to the formation of a flocculent precipitate when the dye was added to the solution. Acid dyes, because of their greater solubility and lower sensitivity to the action of acid or alkali, were not affected to any great extent.
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The triphenylmethane dyes as a class were found to give the best results because of their high tinctorial power. Greater concentrations of the yellow dyes were required in most cases because of their low covering power. Monoammonium phosphate proved to be the most difficult to color. The estimated cost of the dye required to impart a satisfactory color to a ton of any of the materials varied from 7 to 58 cents. Acknowledgment Grateful acknowledgment is made to W. H. ROSS, of this bureau, for his advice and suggestions during the course of this investigation. The authors also wish to acknowledge with thanks the assistance of the following dye manufacturers, who furnished dye samples and information upon which cost estimates were based: National Aniline and Chemical Co., 40 Rector St., New York; E. I. du Pont de Nemaurs and Co., Wilmington, Del.; and Newport Chemical Works, Inc., Phssaic, N.J. Literature Cited (1) 1. G. Parbenindustne Akt.-Ges., French Patent 674,217 (Oct. 15. 1929); Canadian Patent 308,130 (May 27, 1929). (2) Society of Dyers and Colourists, “Colour Index,”
Bradford, Yorkshire,
1924.
Net and Gross Heating Values’ Their Definition and Proper Use Horace C. Porter 1833 CHESTNUT ST.,PBILADELPHIA, Pa.
H
EATING values of solid, liquid, and gaseous fuels are generally, in this country, quoted as the gross values obtained by the laboratory calorimeter. These values include the heat derived from condensation of water formed by combustion (as well as of the original moisture in the fuel), this water ranging in amount from 40 to 50 per cent in the case of solid fuels, to 100 or 110 per cent for liquid, and 200 per cent for gaseous. Therefore the amount of heat, derived from this source, but almost never realized in any degree of practice, is very appreciable, ranging from 500 to 550 B. t. u. per pound for solid fuels, to 1000 to 1200 for liquid, and 2100 for gaseous. Accordingly, some authorities believe that it is more reasonable, in considering relative efficiencies in the use of fuels, not to charge the gross heating value, which is really not a true measure of inherent fuel value, against the fuel but only the net value which expresses properly the fuel value without inclusion of latent heat of condensation. I n 1928 the World Power Conference a t its meeting in London took up this matter and by resolution called representatives of the different countries into conference on the question a t the Berlin meeting in 1930. This resulted in a further resolution requesting the properly constituted standardizing bodies in each of the various countries to assist in creating international standard definitions for the terms “gross” and “net” calorific value. A subcommittee of the American Society for Testing MateriaIs has therefore been appointed under the chairmanship of the author to undertake the fixing of a standard definition for the terms. There are likely to be misunderstandings of what meaning is 1 Received August 11, 1931. Presented before the Division of Gan and Fuel Chemistry at the Sand Meeting of the American Chemical Society, Buffalo, N. Y.,August 31 to September 4, 1931.
conveyed by the term “net heating value.” In this country the term has been commonly understood to mean a value lower than the total or gross value by an amount resulting from one single correction factor-namely, that depending on the water formed in combustion. The standard A. S. T. M. method for determining calorific value of coal and coke (1) now prescribes for deriving net calorific value a deduction of 1040 B. t. u. for each pound of water formed. This is an arbitrary and approximate correction, and may or may not give the excess heat obtained in the bomb method a t constant volume over that obtainable at constant pressure without condensation of water. Similarly there is a correction applied for the higher oxidation of sulfur that occurs in the bomb a8 compared to what takes place in ordinary combustion in air, but this has been considered as necessary even in deriving the gross value. There is a tendency sometimes, however, to interpret net heating value as effective heating value realizable under ideal conditions of practice. This is illustrated by the recommendations of the German national committee of the World Power Conference made June 20, 1930, reading as follows: “The application of two different standards of measurement is recommended*** Btandard of measurement A and standard of measurement B, respectively, and which of the two should be applied depend8 on whether the whole potential quantity of heat or fuel is to be measured, or whether that quantity of heat that is available according to the proces~of application is to be measured.” This clearly implies that the lower or net heating value is to express the quantity of heat made effective under the conditions of practical application of the fuel. Such an interpretation of net heating value would be difficult of standardization. There would arise the necessity
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INDUSTRIAL A N D ENGINEERING CHEiMISTRY
for reaching an agreement on what practical conditions can be considered as ideal or representing best practice. The heat losses, for instance, that may be considered as necessary and unavoidable in the burning of fuel under boilers are not capable of being fixed or standardized. On the other hand, it may perhaps justly be questioned whether, as now recommended by the A. S. T. M. methods, the net heating value should be derived by deduction of the full quantity of the latent heat of vaporization of water at the temperature to which the bomb is cooled after combustion. Lichty and Brown (2) derive thermodynamically an average value of 970 inst.ead of 1040 B. t. u. per pound of water condensed as being the correct average heat given up in the bomb by the water in condensing, over and above what would be given up hypothetically if it were cooled without condensation. This latter basis, they say, is the correct one on which to establish net calorific value. It remains more or less of an arbitrary matter, and it can hardly be said that any one factor is more correct or more reasonable than another for deriving an arbitrarily defined value. The intention is to have this arbitrary deduction
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from the gross value represent as nearly as possible the heat derived from water in the products, and to many it will appear that this heat should be taken as the total derived in the bomb from cooling and condensing the water formed. An illustration may be taken of a lignite containing 25 per cent moisture, and hydrogen sufficient to bring the total water formed in combustion to 60 per cent; or a sugar waste or distillery slop containing 38 per cent moisture and forming a total of 75 per cent water when burned. Should a boiler or other industrial heating device using such materials be charged with the gross heating value in considering efficiency of its performance? And yet, should not the fuel be charged with the gross when there is a question of relative efficiency of the fuel's performance? Also when comparing, in general, fuel values of such materials with those of higher-grade materials, such as coal, would not the net values give a truer relative valuation? L i t e r a t u r e Cited (1) Am. Soc. Testing Materials, Standard Method D 271-30,1930Standards, II,.725. (2) Lichty and Brown, IND. END.&EM., 23, 1419 (1931).
Some Problems in LubricationIof Rocker Arms' E. W. Zublin TEXAS PACIFICCOAL & OIL CO., FORTWORTH, TEXAS
OMMERCIAL airline operators have reported repeatedly that trouble is being had with the lubrication of rocker arms and the ball ends of the push rods. Most of the airport engineers admit that the trouble is due to faulty design rather than to poor qualities of the greases employed. This, howeuer, does not remedy the situation, as they have to maintain their flying schedules with present-day equipment and provide the maximum possible safety. Owing to economic conditions, the companies have been forced to reduce the operating overhead to a minimum, and one step in this plan for greater economy has consisted of lubricating the rocker arms and pulling the push rods of the engines at increasing time intervals. Less than 3 years ago, 10-hour service between the pulling of the push rods was considered excellent. Now, in some places, a minimum of 40 hours is required. Greases must be such that the balls of the push rods do not run dry within the specified period. Squeaking caused by the movement of the balls in the rocker-arm cups indicates absence of lubricant.
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larger air-transportation companies revealed that the different sections employ different types of greases, and that what is good for one seems to be useless for the other. Aluminumsoap greases, with their peculiar increase in consistency in the range from 100' to 250' F. (37.8' to 121.1" C.), appear especially suited to comply with the first five demands and in particular they will resist the tendency to run off except a t temperatures above 300 ' F. (148.9 C.). However, hydrolysis frequently causes them to break down, and this trouble is so serious that some mechanics will reject any grease that becomes rubbery when heated with a match on a thin metal plate. They believe that this rubbery consistency is the cause of the failure to maintain lubrication, not realizing that it is the greatest virtue possessed by aluminum-soap greases, and that the cause of the trouble lies in the breakdown of the soap. Samples of broken-down greases, when examined under the microscope, showed the characteristic floccules of aluminum hydroxide. Field Experience
Required Properties
Greases used for this type of lubrication should combine the following properties:
(lo)
They must be soft; minimum, 300 penetration a t 77' F. (25 C.). (Softness is required to avoid damage to the roller bearings when charging same.) (2) They must lubricate a t 0' F. ( -17.8' C.). (3) They must lubricate a t 350' F. (176.7' C.) (4) They must not gum or carbonize at 350' F. (176.7' C.); ' (5) They must not run off a t any temperature between 0 and 350' F. (-17.8' and 176.7" C.). (6) They must be fairly resistant to moisture; they should not hydrolyze into aluminum hydroxide and free fatty acid. (7) They must not break down under the consistent pounding effect of the push rods on the rocker arms.
There is probably no single grease that will answer all seven demands. An investigation into the practices of some of the I Received August 24, 1931. Presented before the Division of Petroleum Chemistry at the 82nd Meeting of the American Chemical Society, Buffalo. N. Y..August 31 to September 4, l e a l .
At an Atlantic seaboard airport, aluminum-soap greases are employed for the roller bearings of the rocker arm proper, while the ends of the push rods are dipped into a special soda-soap grease before being put into place. This combination is said to give minimum service of 40 hours and service up to 60 hours under the prevalent climatic conditions. At a midwestern airport, in the same kind of equipment, the foregoing combination was tried and was reported t o have failed after less than 20 hours. Soft petrolatum mixed with 150/160 bright stock is preferred, though only 20 hours of service are obtained. At a southern airport good service is obtained by using a straight aluminum-soap grease. Twenty hours are required. High temperature and absence of moisture are the outstanding climatic influences in this section. Hydrolysis causes the same greases to fail in other parts of the country. Reports from a southwestern airport indicate results similar to those obtained in the southern division. Service of
