stream through the solid material; a mere passage over its surface is neither efficient nor economical of material. DISPOSITION OF PURIFYING MATERIAL.--Although much has been written, and some exaggerated claims made, about the maximum, volume of acetylene a certain variety of purifying material will treat, little has been said about the method in which such a material should be employed to obtain the best results. If 1 lb. of a certain substance will purify 200 cubic feet of normal crude acetylene, that weight is sufficient to treat the gas evolved from 40 lb. of carbide; but it will only do so provided it is so disposed in the purifier that the gas does not pass through it at too high a speed, and that it is capable of complete exhaustion. In the coal- gas industry it is usually assumed that four layers of purifying material, each having a superficial area of 1 square foot, are the minimum necessary for the treatment of 100 cubic feet of gas per hour, irrespective of the nature of the purifying material and of the impurity it is intended to extract. If there is any sound basis for this generalization, it should apply equally to the purification of acetylene, because there is no particular reason to imagine that the removal of phosphine by a proper substance should occur at an appreciably different speed from the removal of carbon dioxide, sulphuretted hydrogen, and carbon bisulphide by lime, ferric oxide, and sulphided lime respectively, Using the coal gas figures, then, for every 10 cubic feet of acetylene generated per hour, a superficial area of (4 x 144 / 10) 57.6 square inches of purifying material is required. In the course of Keppeler's research upon different purifying materials it is shown that 400 grammes of heratol, 360 grammes of frankoline, 250 grammes of acagine, and 230 grammes of puratylene each occupy a space of 500 cubic centimetres when loosely loaded into a purifying vessel, and from these data, the following table has been calculated: __________________________________________________________ | | | | | | | Weight | Weight | Cubic Inches | | | per Gallon | per Cubic Foot | Occupied | | | in Lbs. | in Lbs. | per Lb. | |_____________|____________|________________|______________| | | | | | | Water | 10.0 | 62.321 | 27.73 | | Heratol | 8.0 | 49.86 | 31.63 | | Frankoline | 7.2 | 41.87 | 38.21 | | Acagine | 6.0 | 31.16 | 55.16 | | Puratylene | 4.6 | 28.67 | 60.28 | |_____________|____________|________________|______________|