been observed at 140° C., the flame, in a second experiment, has to be removed at 100° or 80° C. The stirring apparatus is then set in motion and igniting experiments commenced at 120° or 100° C., as the case may be. If the flashing point lies

near the admissible limit it is advisable to control the determination by a second test. In all other cases one test suffices if

executed carefully and in accordance with the directions given above.

The size of the igniting flame has no perceptible influence upon the results, but it is recommended to be set in all experiments the size of a pea, since the appearance of flashing is more clearly perceptible with a small flame. Filling the oil holder up to the mark must be strictly adhered to.

To obtain a picture of the reliability of the method, repeated experiments were made with the same oils and the results tabulated in Table I, together with those obtained by slow heating without stirring. It will be seen that with constant stirring of the oil and rapid heating the same results are obtained as with slow heating, and hence that by agitation overheating of some parts of the oil is avoided. The table also shows the faulty determinations obtained by too rapid heating without the use of a stirring apparatus.

Preparatory Experiments for the determination of the flashing Points with Pensky's

Table II treats of the influence or these yong fame, as vel as of the depth of the oi E INGET that the results are not, to any extent. mfuencer by me frst factor, while filling the oil-holder below the mar considerably rases the facing point.

Hence, filling the ni-nvoer op to

the mark has to be strictly adhered to.

Variety and

Mark of the

Sample

Number of the

experiment.

TABLE IL.

Flashing pon С

Normal exper- Fiame double Oi-touter file: Di-anter fied

Mineral oil 19.

135

138

154

Mineral oil

Mixture of

110

2

110

113

115

I and pe

troleum.

109.5

Since oils containing water yield faulty results, they have to be freed from it before subjecting them to the test.

In Table III, the results of experiments made by Holde with 40 varieties of oil, are tabulated and show the great variations in the determination of the flashing point by Pensky's improved apparatus and by open dishes. The magnitude of these variations obtained by the use of different methods shows the necessity of a uniform method.

Apparatus.

TABLE III.

Comparative Tests Between the Older and more Recent Methods.

Flashing point in ° C.

a. Pure mineral oils (arranged according to rising flashing points).

Marks of the samples.

27° 47° 47′ 47° 47° 47° 47° 479 47 47 47P 47 47 10 47 47

140 141 173 157 170 166 164 162 165 164 162 162 168 176 167 170 175 171 166 171 185 190 190 192 192 193