The following substances were used:

1. Oxygen gas, as described above.

2. Hydrogen peroxide, used in 10 percent sol. in the digest, i. e.

approximately 25 cc. to 250 cc. of brei. The liquid was used from a small, hitherto unopened bottle, purchased locally.

3. Sodium peroxide, 5 percent sol.

4. Benzoyl peroxide synthesized in the laboratory from benzoyl chlorid and hydrogen peroxide by the Schotten-Baumann procedure 11, 12 of benzoylating; 5 percent sol.

5. Potassium permanganate, I percent sol. with the digest. The results for autolysis are given below, 13 as cc. of n/5 ammonium hydroxid sol.

Condition

Control.

Benzoyl peroxide....

Sodium peroxide.

Hydrogen peroxide.

Potassium permanganate..

ELECTRIC APPARATUS FOR THE AUTOMATIC CONTROL OF THE FLOW OF GAS

SERGIUS MORGULIS

(U. S. Bureau of Fisheries and the Biochemical Laboratory of Columbia University, at the College of Physicians and Surgeons, New York)

(WITH PLATE 2)

(Received for publication, May 1, 1916)

There are many occasions in laboratory procedures when the automatic regulation of a gas current is highly desirable. This is particularly true of metabolism experiments where, for instance, oxygen must be supplied as rapidly as it is being used up by the organism. To insure a continuous and sufficient supply of oxygen in experiments of long duration, the attention of a special assistant is not infrequently required.

Being engaged, at present, in the construction of a respiration apparatus for the study of the gaseous metabolism of aquatic animals, attempts have been made to introduce, wherever possible, automatic regulators as time saving, as well as trouble saving, devices. In this note I wish to describe briefly an electrically controlled apparatus by means of which the admission of oxygen from a cylinder is effected automatically; and, while this has been designed for a special purpose, it is believed that the apparatus may be easily adapted to other laboratory uses.

The apparatus consists of three essential parts: a "pinch-cock," electromagnets and contact-makers (Plate 2). These will be described separately.2

A side view and top view of the first two parts are shown in 1 Published by permission of the Commissioner of Fisheries.

VIP

Figs. I and 2. The "pinch-cock" consists of a movable frame e, f, g, h, supported by two uprights, c and d, and two brass bars, a and b. The former is permanently fixed to the parallel rods, g and h, by means of pins. The latter, b, can be shifted freely over the rods, g and h, and is attached to j, which can be moved either way in a horizontal plane by means of the set screws k and l. A rubber tube, held in position by two supports, n and o, as can be seen in Fig. 2, passes between the bars a and b, the inner faces of which

are rounded off so as not to injure the rubber tube. The lumen of the tube may be left entirely open, or it may be entirely closed, by varying the distance between the bars, a and b, with the set screws. In this way a permanent flow of gas at any desired rate can be secured. A further increase in the rate of delivery, or a complete shutting off of the current, is effected by shifting the frame, e, f, g, h, to the right or left. These movements are controlled by oppositely-placed powerful electromagnets. When the opening between the horizontal bars, a and b, has been once adjusted, it remains unchanged because on the one hand the set screws hold bar b securely fixed, while bar a, which is attached to the frame, is maintained in a fixed position by the catch m. By lifting that catch,

the entire frame shifts to the left, owing to the elasticity of the springs that extend between a and d; and a decompression of the lumen of the tube is thus effected. By pulling the frame from the opposite side, a and b are brought temporarily close together, compressing the lumen of the tube. This compression lasts only so long, however, as the pull is exerted upon the frame at f; for, as soon as the pull is released, the frame strikes back to its former position by the action of the springs, until it is checked by the catch m.

It is clear, from this description, that a current of gas under a pressure of, say, 2 to 4 lb. may be made to flow at a minimum rate, regulating this with the set screws; and, if necessary, the flow may be temporarily increased to its maximum capacity or temporarily cut off. It is also clear, of course, that if the set screws are adjusted so as to close off the lumen of the tube only two possibilities will be open; namely, the maximum delivery of gas, alternating with complete cessation of the flow. According to the special requirements of the case, either the three-phase or the two-phase regulation may be employed.

The electromagnets which control the movements of the frame, e, f, g, h, are mounted, together with the "pinch-cock," on a brass plate, as may be seen from Fig. I and 2. The construction of these electromagnets is somewhat peculiar and is calculated to obtain a maximum efficiency. The magnet consists of an L-shaped iron base, p, to which a 3/8 inch plate, r, also of iron, is pivoted so that it describes an arc in moving from the vertical to the horizontal position. A stout iron axis tapering at one end is firmly fixed to the vertical part of the base, and on this axis is set a spool bearing numerous windings of fine wire. The free tapering end of the axis fits into a pit of similar shape drilled into the movable iron plate. When an electric current is sent through the spool, the plate is very powerfully attracted to the axis and, owing to the fact that the pointed end protrudes into the plate, a strong pull is exerted from the start. The position of the movable plates from the frame, e, f, g, h, the amplitude of the pull, as well as the return to the original position when the electric current is discontinued, are secured by means of screws and springs, as is shown in Fig. 1 and 2. Each of the iron plates, r, bears upon its free surface a yoke-like structure, s, by means of

which it is interlocked with the frame, e, f, g, h. When the plate, 12, is attracted, the yoke, s2, moving upwards opens the catch, m, held down firmly by a spring. This causes the frame to shift to the left, as already explained, allowing an increased delivery of gas. This side movement of the frame brings bar f close to the cross piece of the yoke, s, of the opposite electromagnet. When this magnet is activated and attracted to the iron axis, it pulls strongly on the frame, shifting it back to the right and the catch, m, again clutches the bar, e, preventing the frame from striking back.

We have yet to consider the contact-makers, which, according to circumstances, bring into play either one or the other electromagnet. In the respiration apparatus I utilize, for this purpose, the spirometer, which is a light aluminum bell floating in a water-jacket formed by two concentric metal pipes. The bell, being exactly counterpoised, responds very quickly to changes in the volume of the air, dropping when the volume is diminished by the using up of oxygen, for instance, and rising when the volume increases. A small metal rod is soldered to the edge of the top of the bell, as will be seen from Plate 2, which passes through a narrow slit in the frame upon which the spirometer bell (6) is suspended. Two hard rubber blocks are attached to the frame: one (3) very near the base is fixed permanently, while the other (4) can be moved the entire length of the frame by means of a continuous screw (5). In this way any distance may be set between these two blocks. On the top of each block there are two little holes filled with mercury which is in contact with binding posts for the electric wires on either side of the block. The contact is effected by a small metal fork (8) with platinum teeth, which moves on a fulcrum set in the middle of the block. One end of the fork is made sufficiently heavy so that the part bearing the platinum points is always raised. When the spirometer bell, moving downwards, reaches a very low level, it presses with its hook-like projection upon the fork and causes its platinum points to dip into the mercury cups, thus closing the contact and sending the current through the left electromagnet. This releases the catch, m, and the tube is decompressed. The oxygen flows, now, at a maximum rate and the spirometer bell fills up rapidly, rising to the level at which the moveable contact-block has been set. As soon as it reaches this