Weighing bottles of polystyrene have now been brought on to the market *. The attractive features of this new product are the unbreakability and the lightness of the material (s.g. x.05), and the relatively low price. The covers fit well and are interchangeable. According to the manufacturers polystyrene does not react with petroleum ether, alcohols, glycols, fats, weak acids and alkalis. As a counterpoise to these advantages, they also state that the material becomes soft above 80" C and is attacked by benzene and other aromatic hydrocarbons, chlorinated hydrocarbons, ketones, esters, ether, tetralin, decalin, strong sulphuric and nitric acids, and other less common substances.
Before using weighing bottles of new material, one must be sure that chemical agents can not alter their weight. The action of water, acids, alkalis, and many other substances on polystyrene has already been investigated a number of times in connection with its technical applications 1-u. If however it is desired to know exactly how great are the errors which can result from the use of polystyrene weighing bottles in the analytical laboratory, then the literature does not offer a complete answer, and it is necessary to carry out special weighing tests under exactly the same conditions as when the weighing bottles are used in the laboratory. We have carried out such tests, with the following results.
We used two types of weighing bottles, mat and transparent, both 50 mm high and of 25 mm cross-section. Their total surface, internal plus external, including the cover, amounted to 1x8 sq.cm, and their weight about 6.8 or 7.8 g.
One weighing bottle of each type was exposed to gases and liquids as described in Table I. The covers were only placed on the bottles at the moment of weighing, otherwise they were placed by the bottles. The weighing of the bottles, after they had been exposed to the action of the gas or liquid, was done in four ways: a) as quickly as possible after taking out of the space in which the bottle was in equilibrium (weights previously placed on the balance), + Townson & Mercer, Ltd., Croydon, injection moulded, S 155. England. Polystyrene weighing bottles, Iteferences p. 462.