From: Oxygen in Therapeutics.  By Clyde E. Ehinger.  1887, page 65.

“For administering the combined gases after the method of Doctor Wallian, at least three gasometers are necessary; one for storing the pure nitrous oxide, another for pure oxygen, and a third for a modified mixture.

“It is possible to make one or two gasometers server the purpose, but it will not be found economy to do so, as such an arrangement will necessitate much extra work, and be a constant source of annoyance. One of the greatest objections to having but one or two gasometers is that a supply of both gases – unmixed – cannot be kept on hand – an almost fatal defect, as emergencies are constantly arising which require one or the other of the pure gases.

“The gasometers may be made of zinc or galvanized iron; the latter material, on account of its strength and durability, is preferable for the larger sizes. By using large gasometers it will not be necessary to generate so frequently.

“To a physician who has not a competent assistant to whom he can entrust the generation of gases and care of apparatus, the size of the gasometers will be found a most important item, as much of his time will be consumed in preparing chemicals, generating and commingling the gases.

“For an ordinary practice I would not advise gasometers of less than seventy-five gallons capacity, and where but three are made use of, it would be better to have the one which is used for storing the commingled gases with a capacity from 100 to 150 gallons.”