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SUMMARY.

The greatest fault of this apparatus is the fact that it is almost impossible to adjust the stopper in the tube so that it will blow out and not cause the flame to be ejected from the valve at the side. A larger water-bath would also be an improvement to this apparatus; and a better means of getting the flame into the lamp to ignite the vapor is also necessary.

This apparatus could be so modified as to cover almost all the requirements of a good tester.

In using this tester it was noticed that sometimes the vapor had not force enough to drive out the stopper but the whole interior of the apparatus was filled with flame. It appears to be necesary to have just the right admixture of vapor and air to eject the stopper.

Another difficulty with this tester, which also applies to several others, is that the distance between the flame of the spirit-lamp and the bottom of the water-bath is too small and the cold metal often extinguishes the spirit-lamp by cooling the flame rapidly.

Since the thermometer is set into a tube closed at the lower end and only receives its heat by conduction through this tube and some oil into which it dips, this method of recording the temperature is objectionable as the rate of conduction is slow.

XI. FOSTER'S AUTOMATIC (OHIO STATE) TESTER.

In this, as in the other testers, we have a water-bath and oil cup Both of these have good well defined filling guages; and the oil-cup is covered. The horizontal cross sections of both water-bath and oilcup are ellipses. In the cover of the oil-cup there are two openings; into one of these passes the thermometer leaving a space around it, and in the other is a tube carrying a wick which dips into the oil-cup. The wick in the small tube is ignited at a given temperature and causes a current down the space around the thermometer and up around its own flame. When vapor rises the jet ignites it and its explosion extinguishes the jet, thus becoming an index of the flashing-point of an oil.

Fosters Automatic (Ohio State) Tester, one-third actual size.

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Oil-cup has elliptical horizontal section and water-bath and outside jacket take the same form. A. Oil-Cup. B. Water-bath. C. Jacket. D. Flash jet.

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In using this tester some very important defects have been noted. In the first place, it does not matter much whether the flash-jet is lit at 100° Fahrenheit, as given in the directions, or at the beginning of the experiments; the results are not very concordant in either case, as may be seen from an inspection of the table. But what is more important than this is the fact that a lower flash-point can be obtained with this apparatus by not lighting the flash-jet and using a small (inch) gas-jet as a means of igniting the vapor. This was found to be true in every case, and goes to prove that the flame in the wick -tube of the apparatus simply causes a current over the surface of the oil, which carries off the vapors mixed with too much air to cause an explosion until they become of considerable density. This apparatus has some good points. It holds considerably more oil than oil testers generally; its well-defined filling guages are to be admired, and the adjustable spirit-lamp for heating the water-bath is too seldom seen. with oil-testers to pass it without commendation. Nevertheless the apparatus fails as a safety oil-tester, since it is little better than an open tester, as can be seen from the experiments with it.

XII. SALLERON-URBAIN (PARIS) APPARATUS.

In his apparatus an effort has been made to ascertain the safety of kerosene oil by determining the tension of the vapor of a sample at a given temperature. It is claimed by the inventors that the lower the flashing poiut of the oil the greater the tension of its vapor at any given temperature. The apparatus consists of a shallow circular metallic vessel having a spindle in the centre, a cover through which passes a manometer tube and thermometer; this cover also contains two other openings. Upon the top of the cover a heavy metal tube is fitted, which works horizontally upon the spindle that passes several inches above the upper surface of the cover of the apparatus. This last tube is so arranged that by moving it through a small are upon the spindle an opening below may be closed or opened at will. A solid plunger is fitted through another opening in the cover; and a screw cap to the heavy movable tube completes the apparatus.

To use this apparatus, the cover is placed upon the shallow vessel and contains the manometer tnbe, thermometer and plunger, all tightly screwed into stuffing boxes; upon the spindle is now placed the movable heavy tube in such a position that the opening into the cover below is free. By means of a pipette fifty cubic centimeters of water are run into the shallow vessel through the heavy metal tube, the tube is moved through its arc and the opening below closed. The tube itself is now filled with the oil to be tested, the cap upon the oil-tube screwed down tight, and the whole immersed in water till the thermometer reads fifteen degrees Celsius. At this temperature, the plunger is screwed down until the water in the manometer tube stands at zero. The oil tube is now moved back through its arc and the oil it contains falls into the water below, the column in the manometer tube rises and gives in millimeters the tension of the vapor of the oil for that temperature. From a number of experiments by the inventors, a tension of sixty-four millimeters of water at fifteen degrees Celsius is considered the minimum allowable for a safe oil,

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