The Addition of Bromine to Crotonic Acid and to Ethyl Crotonate under Various Conditions

Many chemical and physical reactions are accompanied by changes in weight of the reactants due to evaporation of liquids, evolution of gases, or adsorption of gases. Studies are made using data which show the manner in which the weight changes with time. Kinetic studies are made from a knowledge of the rate of loss or gain of a component. The drying of a precipitate to constant weight involves a loss in weight. Rates of evaporation of liquids from different types of surfaces involve changes of weight as a function of time. Several instruments and methods are used to follow weight changes. Gas buret systems are used to measure the volume of a gaseous component which is adding to or subtracting from the weight of a reactant. The ordinary analytical balance is used to follow weight changes by making intermittent weighings. This latter method involves tedious operations and interruptions of the treatment of the reactants. Effort has been put forth to devise instruments which will automatically weigh substances and record these weighings on some type of graph. Gregg and Wintle (1) devised a glass automatic electrical sorption balance. Gregg (2) later described a recording system for this type balance. Eyrand (3) reported a glass sorption balance of a somewhat different type. Duval (4) described a thermal balance that automatically records changes in weight on film. Described in this paper is an instrument attached to a modified ordinary analytical balance which automatically records on graph paper changes in weight as a function of time