a. Tests of Standards of Capacity Calibrations are made by the Bureau on capacity standards that are in the customary units of trade, that is the gallon, its multiples, and submultiples, or in metric units. Furthermore the Bureau calibrates precision grade volumetric glassware which is normally in metric units. Tests are made in accordance with test-fee schedules, copies of which may be obtained by application to the Bureau. 3.5. Maintenance and Preservation of Fundamental Standards of Length and Mass There is considerable interest in the maintenance and preservation of the national standards of length and mass at the National Bureau of Standards. In 1955, a special glass door. fully protected by an alarm system, was installed so that during the regular working hours of the Bureau the vault can be viewed by those interested. At other times the steel outer doors are locked. All measurements made with these standards are conducted in special air-conditioned laboratories to which the standards are taken a sufficiently long time before the observations to ensure that the standards will be in a state of equilibrium under standard conditions when the measurements or comparisons are made. Hence it is not necessary to maintain the vault at standard conditions, but care is taken to prevent large changes of temperature. More important is the care to prevent any damage to the standards because of careless handling. 4. Weights and Measures in Everyday Life As weighing and measuring are important factors in our everyday lives, it is quite natural that questions arise about the use of various units and terms and about the magnitude of quantities involved. Only two items will be considered here, first the weight of coal, and second the definitions and usages of the terms "ton" and "tonnage." 4.1. Weight of Coal Questions are frequently asked about the weight per unit volume of coal. As there are large variations in the weight per cubic foot of coal, the reader is cautioned that the figures presented herein are only approximate values, and that in the case of any particular delivery of coal, the actual number of cubic feet per ton (of 2 000 pounds), may differ materially from the values given here. The following values may, however, be satisfactory for use in calculating the approximate size of bin required to contain a given number of tons of coal, the approximate number of tons of coal that a given bin will contain, and the approximate weight of a measured amount of coal. Relatively large shortages can be detected by computing the weights of deliveries, and computed weights may properly be used by a purchaser as a basis of complaint to the weights and measures official; such evidence alone, however, probably would not be accepted by a court, and satisfactory evidence can be procured only by actually weighing the coal comprising a delivery. The weight per cubic foot of anthracite (hard coal) varies with the size into which the coal is broken, and with the kind of coal or the vein from which the coal comes. According to information published by the Anthracite Institute, "frequently used average weight and volume figures for all sizes of anthracite are 37 cubic feet per ton and 54 lbs per cubic feet." This corresponds to 67 pounds per stricken bushel (2 150.42 cubic inches). Variations from these averages as high as 10 percent may be expected. The weight of bituminous (common soft) coal also varies according to the locality from which the coal comes. Such weights range from 47 to 55 pounds per cubic foot. These values correspond to 42.6 to 36.4 cubic feet per 2 000-pound ton; and to 58.5 to 68.4 pounds per stricken bushel. 4.2. Definitions and Usages of the Terms "Ton" and "Tonnage" Because the words "ton" and "tonnage" are used in widely different senses, a great deal of confusion has arisen regarding the application of these terms. 16 a. Definitions and Uses of "Ton" The ton is used as a unit of measure in two distinct senses: (1) as a unit of weight, and (2) as a unit of capacity or volume. In the first sense the term has the following meanings: (a). The short, or net ton of 2 000 pounds. (b). The long, gross, or shipper's ton of 2 240 pounds. (c). The metric ton of 1 000 kilograms, or 2 204.6 pounds. In the second sense (capacity) it is usually restricted to uses relating to ships and has the following meaning: (a). The register ton of 100 cubic feet. (b). The measurement ton of 40 cubic feet. (c). The English water ton of 224 British Imperial gallons. In the United States and Canada the ton (weight) most commonly used is the short ton, in Great Britain it is the long ton, and in countries using the metric system it is the metric ton. The register ton and the measurement ton are capacity units used in expressing the tonnage of ships. The English water ton is used, chiefly in Great Britain, in statistics dealing with petroleum products. There have been many other uses of the term ton such as the timber ton of 40 cubic feet and the wheat ton of 20 bushels, but their use has been local and the meanings have not been consistent from one place to another. b. Definitions and Uses of "Tonnage" Properly, the word "tonnage" is used as a noun only in respect to the capacity and dimensions of ships, and to the amount of the ship's cargo. There are two distinct kinds of tonnage, namely, vessel tonnage and cargo tonnage and each of these is used in various meanings. The several kinds of vessel tonnage are as follows: Gross tonnage, or gross register tonnage, is the total cubical capacity of a ship expressed in register tons of 100 cubic feet, or 2.83 cubic meters, less such space as hatchways, bakeries, galleys, etc., as are exempted from measurement by different governments. There is some lack of uniformity in the gross tonnages as given by different nations on account of lack of agreement on the spaces that are to be exempted. Official merchant marine statistics of most countries are published in terms of the gross register tonnage. Press references to ship tonnage are usually to the gross tonnage. The net tonnage, or net register tonnage, is the gross tonnage less the different spaces specified by maritime nations in their measurement rules and laws. The spaces that are deducted are those totally unavailable for carrying cargo, such as the engine room, coal bunkers, crews quarters, chart and instrument room, etc. The net tonnage is used in computing the amount of cargo that can be loaded on a ship. It is used as the basis for wharfage and other similar charges. The register under-deck tonnage is the cubical capacity of a ship under her tonnage deck expressed in register tons. In a vessel having more than one deck the tonnage deck is the second from the keel. There are several variations of displacement tonnage. The dead weight tonnage is the difference between the "loaded" and "light" displacement tonnages of a vessel. It is expressed in terms of the long ton of 2 240 pounds, or the metric ton of 2 204.6 pounds, and is the weight of fuel, passengers, and cargo that a vessel can carry when loaded to her maximum draft. The second variety of tonnage, cargo tonnage, refers to the weight of the particular items making up the cargo. In overseas traffic it is usually expressed in long tons of 2 240 pounds or metric tons of 2 204.6 pounds. The short ton is only occasionally used. The cargo tonnage is therefore very distinct from vessel tonnage. 5. General Tables of Weights and Measures These tables have been prepared for the benefit of those requiring tables of weights and measures for occasional ready reference. In section 5.4 the tables are carried out to a large number of decimal places and exact values are indicated by boldface type. In most of the other tables only a limited number of decimal places are given, thus making the tables better adapted to the average user. More extensive tables will be found in Miscellaneous Publication M214 of the National Bureau of Standards, Units of Weight and Measure-Definitions and Tables of Equivalents (sold by the Superintendent of Documents, U. S. Government Printing Office, Washington 25, D. C., at 40 cents a copy). 5.1. Tables of United States Customary Weights and Measures LINEAR MEASURE 12 inches (in.) 1 foot (ft). 3 feet 1 yard (yd). 1 rod (rd), pole, or perch=16%1⁄2 feet. 51⁄2 yards 40 rods 1 furlong (fur.) = 220 yards = 660 feet. 8 furlongs 1 statute mile (mi) = 1 760 yards=5 280 feet. 6 076.103 33 . . . feet (1 852 meters) = 1 international nautical mile. This value was adopted effective July 1, 1954, for use in the United States. nautical (geographical or sea) mile. The value formerly used in the United States was 6 080.20 feet=1 AREA MEASURE 144 square inches (sq in.) = 1 square foot (sq ft). 304 square yards 1 mile square 6 miles square 4 gills (gi) 4 quarts = 1 square yard (sq yd) = 1 296 square inches. = 1 square rod (sq rd) = 2724 square feet. CUBIC MEASURE 1 728 cubic inches (cu in.) = 1 cubic foot (cu ft). =1 cubic yard (cu yd). 1 acre 4 840 square yards=43 560 square feet. = = 1 square mile (sq mi). = 1 section of land. = 1 township=36 sections=36 square miles. LIQUID MEASURE & 1 pint (pt) = 28.875 cubic inches. = 1 quart (qt)=57.75 cubic inches. = 1 gallon (gal) = 231 cubic inches=8 pints=32 gills. • Squares and cubes of units are sometimes abbreviated by using "superior" figures. For example, ft2 means square foot, and ft3 means cubic foot. b When necessary to distinguish the liquid pint or quart from the dry pint or quart, the word "liquid” or the abbreviation "liq" should be used in combination with the name or abbreviation of the liquid unit. In "gross" or "long" measure, the following values are recognized: 112 pounds =1 gross or long hundredweight." TROY WEIGHT [The "grain" is the same in avoirdupois, troy, and apothecaries weight.] 24 grains 1 pennyweight (dwt). 20 pennyweights = 1 ounce troy (oz t)=480 grains. 12 ounces troy = 1 pound troy (lb t)=240 pennyweights=5 760 grains. APOTHECARIES WEIGHT [The "grain" is the same in avoirdupois, troy, and apothecaries weight.] 20 grains 1 scruple (s ap or ). 1 dram apothecaries (dr ap or 3)=60 grains. 1 ounce apothecaries (oz ap or 3)= 3 scruples 8 drams apothecaries 24 scruples=480 grains. 12 ounces apothecaries = 1 pound apothecaries (lb ap or b)=96 drams apothe- 5.2. Notes on British Weights and Measures Tables In Great Britain, the yard, the avoirdupois pound, the troy pound, and the apothecaries pound, are, for all commercial purposes, identical with the units of the same names used in the United States. The tables of British linear measure, troy weight, and apothecaries weight are the same as the corresponding United States tables, except for the British spelling "drachm" • When necessary to distinguish the dry pint or quart from the liquid pint or quart, the word "dry" should be used in combination with the name or abbreviation of the dry unit. d When necessary to distinguish the avoirdupois dram from the apothecaries dram, or to distinguish the avoirdupois dram or ounce from the fluid dram or ounce, or to distinguish the avoirdupois ounce or pound from the troy or apothecaries ounce or pound, the word "avoirdupois" or the abbreviation "avdp" should be used in combination with the name or abbreviation of the avoirdupois unit. • ⚫ When the terms "hundredweight" and "ton" are used unmodified, they are commonly understood to mean the 100-pound hundredweight and the 2000-pound ton, respectively; these units may be designated "net" or "short" when necessary to distinguish them from the corresponding units in gross or long measure. in the table of apothecaries weight. The table of British avoirdupois weight is the same as the United States table up to 1 pound; above that point the table reads: The present British gallon and bushel, known as the "Imperial gallon" and "Imperial bushel" are, respectively, about 20 percent and 3 percent larger than the United States gallon and bushel. The Imperial gallon is defined as the volume of 10 avoirdupois pounds of water under specified conditions. and the Imperial bushel is defined as 8 Imperial gallons. Also, the subdivision of the Imperial gallon as presented in the table of British apothecaries fluid measure differs in two important respects from the corresponding United States subdivision, in that the Imperial gallon is divided into 160 fluid ounces (whereas the United States gallon is divided into 128 fluid ounces), and a "fluid scruple" is included. The full table of British measures of capacity (which are used alike for liquid and for dry commodities) is as follows: 5.3. Tables of Metric Weights and Measures In the metric system of weights and measures, designations of multiples and subdivisions. of any unit may be arrived at by combining with the name of the unit the prefixes deka, hecto, and kilo, meaning, respectively, 10, 100, and 1 000, and deci, centi, and milli, meaning, respectively, one-tenth, one-hundredth, and one-thousandth. In some of the following metric tables, some such multiples and subdivisions have not been included for the reason that these have little, if any, currency in actual usage. In certain cases, particularly in scientific usage, it becomes convenient to provide for multiples larger than 1 000 and for subdivisions smaller than one-thousandth. Accordingly, the following prefixes have been introduced and these are now generally recognized: myria, meaning 10 000, micro, meaning one-millionth. A special case is found in the term "micron" (abbreviated as μ, the Greek letter mu), a coined word meaning one-millionth of a meter (equivalent to one-thousandth of a millimeter); a millimicron (abbreviated as mu) is one-thousandth of a micron (equivalent to one-millionth of a millimeter), and a micromicron (abbreviated as uu) is one-millionth of a micron (equivalent to one-thousandth of a millimicron or to 0.000 000 001 millimeter.) |