Since our first paper1 Venkataramaiah reported3 the independent discovery of the active form of hydrogen, distinguished by its ability to reduce potassium permanganate solution rapidly at room temperature. He produced it first in the alternating current corona, but made the interesting observation that it is produced in measurable quantities when oxygen is exploded in an excess of hydrogen. Since all other methods of its preparation, including those reported below, are dependent on prolonged and intense ionization of the hydrogen, this preparation by explosion is of importance in determining the mechanism of its formation.New Methods of Preparation Siemens Ozonizer.-In view of the read)r formation of the new gas by means of the electrical discharge at 10,000 to 20,000 volts and a current of 4 to 25 milli-amperes, both at atmospheric pressure and at a pressure of 4 to 8 cm. of mercury, there is little new in its successful preparation in the usual quantities of about 0.01% by means of the ordinary Siemens glass tube ozonizer, with external tin-foil electrodes. This method is simple and reliable. It is particularly effective at the temperature of boiling liquid ammonia. This method failed, however, when the ozonizer was immersed in liquid air, probably because of the increased dielectric strength of the glass walls. When metallic electrodes were inserted through the walls of the tube, the low temperature did not prevent the activation.In this, as in all the work, the hydrogen was prepared and purified as described in the previous paper. In all cases the test for activation was the formation of hydrogen sulfide in passage of the gas over cold sulfur. In every case blank tests were made to show that the hydrogen itself, without the ionizing agent, did not attack the sulfur.

The large number of papers on the nature of the photochemical reaction between chlorine and hydrogen is evidence of the fundamental significance of this still unsolved problem. That a reaction takes place, especially under the influence of the shorter wave lengths, and that it is the chlorine which is effective in absorbing the radiant energy is established, but almost every concomitant fact has been repeatedly asserted and denied by various investigators. The recent discovery of the ozone form of hydrogen,1 however, suggests strongly that chlorine also may exist in some similar active modification, and calls for a reexamination of the evidence. The work here reported shows that if such an active form exists at all, it returns to the ordinary form within a very small fraction of a second, but that, nevertheless, an increased activity can be imparted to the chlorine by previous exposure to light such that the period of induction of the photochemical reaction with hydrogen is reduced or eliminated, this condition lasting for hours or days, but not indefinitely.William Cruickshank, who first studied this photochemical reaction, observed2 that the reaction is first hesitant, and requires several minutes before it attains a constant maximum velocity. This "period of indue-'