Influence of atmospheric conditions in the testing of sugars

Abstract

That atmospheric conditions may exert an appreciable effect in the testing of sugar has been vaguely recognized for some years. The magnitude of this influence has, however, never been determined, and it is difiicult to understand how this possible source of error has so long been practically ignored when we consider the large amount of research that has been carried on in an effort to reduce the process of testing to an exact science. Fortunately in the standardization of the saccharimeter, by means of the normal solution of sucrose, all chance of error from atmospheric conditions is eliminated. The normal weight of sucrose is made up to volume, and the polariscope tube is filled, under conditions that eliminate an appreciable change in the concentration of the nrifiltered solution. In the process of testing, these conditions are unavoidably altered. The necessity for clarification requires that the liquid be passed once, and frequently twice, through ordinary filter paper to remove the precipitated impm-ities. While this is being done, there is more or less exposiure to the atmosphere of the laboratory, with a consequent increase in the concentration. Since the rotation observed is directly proportional to the concentration, any change, if appreciable, must either be prevented or a correction applied to the polarization. Browne ^ and other investigators have recommended the use of cover glasses on the funnels to guard against possible evaporation. The process of testing should obviously be such that when applied to the normal sucrose solution the polarization will be IOC on the saccharimeter scale within the limits of accuracy