have much to do with their production; for the proportion of the total phosphorus and sulphur found in the crude gas which exists as "compounds" tends to be greater as the generating plant yields a higher temperature. It should be noted that ammonia and sulphuretted hydrogen have one property in common which sharply distinguishes them from the sulphur "compounds," and from all the phosphorus compounds, including phosphine. Ammonia and sulphuretted hydrogen are both very soluble in water, the latter more particularly in the lime-water of an active acetylene generator; while all the other bodies referred to are completely insoluble. It follows, therefore, that a proper washing of the crude gas in water should suffice to remove all the ammonia and sulphuretted hydrogen from the acetylene; and as a matter of fact those generators in which the gas is evolved in presence of a large excess of water, and in which it has to bubble through such water, yield an acetylene practically free from ammonia, and containing nearly all the sulphur which it does contain in the state of "compounds." It must also be remembered that chemical processes which are perfectly suited to the extraction of sulphuretted hydrogen and phosphine are not necessarily adapted for the removal of the other phosphorus and sulphur compounds. WASHERS.--In designing a washer for the extraction of ammonia and sulphuretted hydrogen it is necessary to see that the gas is brought into most intimate contact with the liquid, while yet no more pressure than can possibly be avoided is lost. Subdivision of the gas stream may be effected by fitting the mouth of the inlet-pipe with a rose having a large number of very small holes some appreciable distance apart, or by bending the pipe to a horizontal position and drilling it on its upper surface with numbers of small holes. Another method is to force the gas to travel under a series of partitions extending just below the water- level, forming the lower edges of those partitions either perfectly horizontal or with small notches like the teeth of a saw. One volume of pure water only absorbs about three volumes of sulphuretted hydrogen at atmospheric temperatures, but takes up some 600 volumes of gaseous ammonia; and as ammonia always accompanies the sulphuretted hydrogen, the latter may be said to be absorbed in the washer by a solution of ammonia, a liquid in which sulphuretted hydrogen is much more soluble. Therefore, since water only dissolves about an equal volume of acetylene, the liquid in the washer will continue to extract ammonia and sulphuretted hydrogen long after it is saturated with the hydrocarbon. For this reason, _i.e._, to avoid waste of acetylene by dissolution in the clean water of the washer, the plan is sometimes adopted of introducing water to the generator through the washer, so that practically the carbide is always attacked by a liquid saturated with acetylene. Provided the liquid