摘要：Determination of an extractable hazardous component from plastic containers or instruments is made by two different methods in the test of the "Specifications and Standards of Containers and Packages, " provided by the Ministry of Health and Welfare. One is the method for containers, into which the extract is filled, and the other is for instruments such as films that are immersed in the extract. In both methods, the amount of the extracted substances is determined per 1000 ml of the extract. In these cases, the ratio of the volume of extract to the surface area of containers is not constant. In fact, it was ascertained that the amount of the extracted substances is not proportional to the volume of the extract but to the surface area. Now we propose that the amount of the extracts should always be determined per unit surface area. For this purpose, a simple and practical method is required for measuring the surface area of various containers, and the authors recommended here a new method, named "Sand gravimetric method." The internal surface of the container is coated with glycerol as thinly as possible, and then covered uniformly with sea sand (80-100 mesh). The surface area can be determined by weighing the sand stuck on glycerol, as the sand weight will be proportional to the surface area. This method is a very accurate and convenient way to determine the surface area of various solids, and is applicable for determination of that of glazed potteries or enamelled vessels for foodstuff.
