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Shows the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) to 3,3',5,5'-tetramethylbenzidine diimine. The resulting one-electron oxidation product is a diimine-diamine complex, which causes the solution to take on a blue colour, [2] and this colour change can be read on a spectrophotometer at the wavelengths of 370 and 650 nm.
English-speaking countries also used a system of units of fluid measure, or in modern terminology volume units, based on the apothecaries' system. Originally, the terms and symbols used to describe the volume measurements of liquids were the same as or similar to those used to describe weight measurements of solids [33] (for example, the pound by weight and the fluid pint were both referred to ...
The pound or pound-mass is a unit of mass used in both the British imperial and United States customary systems of measurement.Various definitions have been used; the most common today is the international avoirdupois pound, which is legally defined as exactly 0.453 592 37 kilograms, and which is divided into 16 avoirdupois ounces. [1]
A US fluid ounce is 1 / 16 of a US pint (about 1·04 UK fluid ounces or 29.6 mL); a UK fluid ounce is 1 / 20 of a UK pint (about 0·96 US fluid ounce or 28.4 mL). On a larger scale, perhaps for institutional cookery, a UK gallon is 8 UK pints (160 UK fluid ounces; about 1·2 US gallons or 4.546 litres), whereas the US gallon is ...
In terms of its physical properties, 4,4'-benzidine is poorly soluble in cold water but can be recrystallized from hot water, where it crystallises as the monohydrate. It is dibasic, the deprotonated species has K a values of 9.3 × 10 −10 and 5.6 × 10 −11. Its solutions react with oxidizing agents to give deeply coloured quinone-related ...
The table of imperial avoirdupois mass is the same as the United States table up to one pound, but above that point, the tables differ. The imperial system has a hundredweight, defined as eight stone of 14 lb each, or 112 lb (50.802 345 44 kg), whereas a US hundredweight is 100 lb (45.359 237 kg). In both systems, 20 hundredweights make a ton.
The weights are in denominations of 7 pounds (corresponding to a unit known as the clip or wool-clip), 14 pounds (stone), 56 pounds (4 stone) and 91 pounds (1 ⁄ 4 sack or woolsack). [ 18 ] [ 19 ] The 91-pound weight is thought to have been commissioned by Edward III in conjunction with the statute of 1350, while the other weights are thought ...
In the apothecaries' system, which was widely used in the United States until the middle of the 20th century, [15] the dram is the mass of 1 ⁄ 96 pounds apothecaries (lb ap), or 1 ⁄ 8 ounces apothecaries (oz ap or ℥) [5]: C-7 (the pound apothecaries and ounce apothecaries are equal to the troy pound (lb t), and troy ounce (oz t ...