468 T H E J O U R N A L OF I N D U S T R I A L

battery were placed on the under side of the table, and the clock with its flexible leads a t any convenient point. This leaves the calorimeter table clear.

The single signal for both “warning” and “reading” has been found perfectly satisfactory.

Attention is called to these modifications to enable small laboratories t o receive the benefits of Mr. Myers’ equipment with somewhat less labor in the construc- tion of the device.

TESTING LABORATORY PUBLIC SERVICE ELECTRIC COMPANY

NEWARK, NEW JERSEY

A DEVICE FOR REMOVING PLUGS FROM STOPCOCKS’ By VERNON C. ALLISON

Received February 1 7 , 1919

It is very annoying to have a stopcock stuck on a piece of calibrated apparatus, or, in these days of high prices, on any piece of apparatus. This fre- quently happens in burettes, separatory funnels, glass set-up systems, and apparatus used in gas analysis work, due t o the use of caustic, bichromate, and many other solutions,

The common method of removing the stuck plug is t o place a small piece of wood on the plug and to more or less gently hammer the wood, resulting in a great many cases in the barrel being cracked, the plug chipped, and, in complex apparatus, breakage of important parts. If, however, a steady pressure is exerted on the plug with the glass in contact with nothing but wood, the plug can easily be removed without damaging either barrel or plug.

74 S/DE EL PVAT/ON SECTION THRU RA

FIG. I-STOPCOCK STEM REMOVER

The two accompanying figures show a device which has been used very successfully a t the Pittsburgh station of the Bureau of Mines. Fig. I shows the device designed to operate over almost any size stop- cock in common use and is constructed of hard maple or lignum vitae, making it very strong and durable. Fig. 2 illustrates the method of applying the steady pressure with a vise in case of loose apparatus. If the stuck stopcock is located on a set-up piece of appara- tus, a U-clamp can be substituted for the vise.

1 Published by permission oE the Director of the Bureau of Mines.

A N D E N G I N E E R I N G CHEMISTRY Vol. 1 1 , No. 5

FIG, %--METHOD O F OPERATING STOPCOCK STEM REMOVER

About 2 0 stopcocks have been removed with this, device with no casualties, and in one instance, 7 stuck stopcocks on burettes were successfully removed i n 4 min.

CHEMICAL RESEARCH LABORATORY PITTSBURGH EXPERIMENT STATXON BUREAU OF MINES, PXTTSBURGH

DATA ON PLATlNUM GAUZE USED AS A CATALYZER FOR THE OXIDATION OF AMMONIA. TABLE OF

WEIGHTS AND ACTIVE SURFACE OF PLAT- INUM, AIR SPACE, ETC., SHOWN FOR

A UNIT OF ONE SQUARE INCH OF GAUZE OF A GIVEN MESH AND

DIAMETER OF WIRE By ALVIN ALLEN CAMPBELL

Received December 14, 1918

The tables listed below are figuied on the basis of one square inch of gauze as a unit. TABLE I-ACTIVS SURSACS OF PLATINUM IN ONE SQUARE INCH OF G A U Z ~

Diam. Wire Pt Surface Mesh Inch sq. In.

80 80

100 120 150 150

0.0026 1.3873 0.0030 1 ,5841 0.0026 1.6951 0.0020 1.4748 0.0015 1.4821 0.0020 1.9573

The first section shows the mesh or number of wires from center t o center each way per linear inch. The mesh should be accurate and can only be made so when woven on an automatic loom.

TABLE 11-WEIGHT PER SQUARE INCH OF G A U Z ~ IN GRAMS Diam. Wire

Mesh Inch Gram Wt. per Sq. In.

80 0,0026 0.33815 80 0.0030 0.46592

100 0.0026 0.42268 120 0.0020 0.29863 150 0.0015 0.2 1009 150 0.0020 0.37329

Under the heading “Diameter of Wire” a factor of error, either plus or minus, must be taken into con- sideration for the reason tha t it would be practically impossible to draw any considerable amount of extra fine wire to a given size with a working tolerance of

May, 1919 T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y 469

O.OOQI in. The factor of error t o be taken into con- sideration would be 0 . 0 2 1 per cent. This figure has been taken from the actual working of many thou- sand ounces of platinum gauze and from the theoret- ical weights should the wire be of correct diameter and exact in size. I t would follow that the factor of error must; be taken into consideration, not only in weight, but in all other calculations.

TABLE 111-AIR SPACE PER SQUARE INCH OP GAUZE Diam. Wire Air Space

Mesh Inch Sq. In. 80 80

100 120 150 150

0,0025 0.0030 0.0026 0,0020 0.0015 0.0020

0.6272 0.5774 0.5676 0.5715 0.5990 0.4886

The active surface per square inch is the actual sur- face of platinum exposed t o the gases being oxi- dized.

It has been state& by some eminent chemists that platinum of the highest purity is necessary to obtain the best efficiency of operation, but this theory seems t o have been disproved by recent experiments in which efficiency of operation as great as that given by pure platinum was obtained by the use of gauze fabricated from an alloy containing gg per cent platinum and I per cent iridium. This alloy has in addition the mechanical advantage that it makes possible the draw- ing of a finer wire and consequently the weaving of a finer mesh.

TABLE IV-SURFACE IN SQUARE INCHES PER CUBIC CENTIMETER OF PLATINUM

Mesh Inch Sq. In. Diam. Wire Active Surface

80 80

100 120 150 150

0.0026 79.9058 0.0030 72.611 1 0,0026 88.0941 0.0020 109.0701 0.0015 154.8643 0.0020 115,3401

There are certain impossible manufacturing condi- tioris in the fabrication from C. P. platinum wire of gauzes of extra fine sizes. While i t is quite possible t o draw and even weave with C. P. stock the very fine sizes, the limit as t o the finest size of the wire used should be set as 0.003 in. diameter; in making finer wire than this the cost of manufacture increases out of proportion with tha t of the finer sizes when a platinum-iridium alloy is used.

TABLE V-ACTIVE SURFACE I N SQUARE INCUES PER GRAM OB PLATINUM Diam. Wire Active Surface

Mesh Inch sq. In. 80 80

100 120 150 150

4.148 3.401 4.013 4.962 7.058 5.243

I n the fabrication or weaving of platinum gauze i t is necessary t o utilize a compensating tension on the warp wires. Owing to this lack of stretch and to the fragility of C. P. platinum, the operation of working with wire finer than 0 .003 in. becomes a very costly operation. By using a platinum-iridium alloy as stated, we find the added cost of drawing and weav- ing eliminated and brought down in line with the graduation of the finer sizes of wire and mesh.

While i t is quite possible to fabricate gauzes from wire as fine as 0.001 in. in diameter, the question con- fronts us as to the strength of the gauze in operation as a catalyzer. We have t o take into consideration the air pressure. Table I11 gives amount of free air space for the different sizes of wire and mesh. How- ever, that is not the only thing which must be taken into consideration. A t a temperature of possibly gooD C. the metal has less resistance t o pressure of air or gases than a t lower temperatures. There is also the change in the surface as it becomes spongy and continues to become more spongy until the gauze lacks power of resistance for further use.

A gauze of C. P. platinum made 80 meshes per inch and fabricated from 0.003 in. wire has shown about 2 5 per cent longer life than a gauze of the same mesh made of 0.0026 in. wire. This additional life is made possible by the greater cubical content and added tensile strength of the platinum wire used. We are told, however, that the catalyzer made of 0.0026 in. wire is more efficient. This is probably due to the difference in cubical contents of the metal used and to the fact that the spongy surface of the lighter wire becomes greater in volume. However, the lighter gauze is very fragile and the greatest care must be exercised in handling it. A gauze made of a mesh of 1 2 0 per inch and of a wire of 0.002 in. diameter, using an alloy of gg per cent platinum and I per cent iridium, has several advantages over the coarser meshes woven of a heavier wire where their use is only for mechanical strength. For instance, the air resistance is about the same for 120-mesh 0 . 0 0 2 in. wire as 80-mesh 0.003 in. wire, the 120-mesh gauze of the platinum-iridium 0 . 0 0 2 in. wire being much stronger than the 80-mesh C. P. platinum 0.003 in. wire, with a showing of better than 60 per cent additional active surface for the same weight of metal. It would follow that the life of a gauze should be increased even beyond that of the 80-mesh 0.003 in. gauze of C. P. platinum. Also, were the finer mesh gauze used, the openings through which the gases pass would be considerably smaller and of a greater number, thereby giving a quicker and more even oxidation, while we have not decreased the air space or increased the resis- tance.

I n compiling the above tables, the writer refers t o the active surface as the entire surface exposed to the atmosphere. Some chemists make the claim that only one-half of the total surface of gauze is active under the oxidation process; we claim that there is no basis for the statement that the entire surface is not active. We know that after the ammonia gases pass through the heated gauze a complete oxidation takes place and theory tells us tha t the greater percentage of change takes place upon contact with the outer side of the catalyst; however, i t would appear that the inner side of the gauze would take care of any incom- plete oxidation of the element. The active surface is therefore figured as being the entire surface of the small wires composing the gauze,

NEWARK WIRE CLOTH COMPANY NEWARK, NEW JERSEY