PREPARATION OF SINTERED PYREX GLASS AERATORS FOR USE IN WATER CULTURE EXPERIMENTS WITH PLANTS

Abstract

In growing plants under water culture conditions it is frequently important, and sometimes indispensable, to pass air under pressure through the solutions. Such aeration has a profound influence on root development. A practical problem arises of providing means for the uniform distribution of air through the culture solution, especially when tanks or other large containers are employed. In some experiments it is also necessary that the aeration devices shall not yield impurities to the solution ; for example, in the study of the effects of elements required by the plant in minute quantity. It has been found essential to the work of this laboratory to provide extensive facilities for aeration in the greenhouse. Several methods of distributing air were devised but were eliminated for various reasons. Among the devices used were surgical rubber tubing; porous porcelain, alundum, and block tin tubing; Folin tubes; and carborundum blocks. Surgical rubber tubing with a soft smooth wall, pierced with fine needle holes, aerated solutions fairly well, but was discarded because of its rapid deterioration, uneven aeration, and compositional impurities. Block tin tubing, drilled with small holes, was rejected because of uneven aeration and possible toxicity. The principal objections to alundum, porcelain, and carborundum were mechanical unsuitability and possible presence of impurities, both in the aerators and in the connections necessarily employed. Since inert, resistant units of uniform quality1 and capable of dispersing the air in fine bubbles were essential, pyrex glass was finally chosen as a suitable medium through which air could be distributed without encountering the objections mentioned. Glass aerators of the type needed were not obtainable on the market, and as methods described in the literature were not applicable to our requirements, it was necessary to develop one. Many modifications of sintered glass aerators were tried, such as sintered disks sealed into glass tubing of various sizes and shapes, and tubing constructed entirely of sintered glass. Individually these were satisfactory in operation, but could not be economically produced in large quantities and it was difficult to obtain even aeration throughout a group of aerators. The method finally devised incorporates the sintering and sealing in one operation. The resulting aerator is efficient, rapidly and easily made in large quantities, and readily cleaned.