Another butter, shown by the microscope to be adulterated, gave—

These results show that the method is capable of general application. Collecting together the mean results obtained with butter-fats the following table is obtained :

TABLE NO. 2.-Melting points, Sc., of butters of doubtful purity.

The above were all bought as pure butters. They are condemned on account of the low percentage of soluble acid, while by their specific gravity they appear to fall near the limit of purity. The soluble acid in the above was determined by washing out and not by Reichert's method.

Table No. 3.—Melting point of substances sold as butter, but proved by analysis to be adulterated.

TABLE NO. 4.—Melting point, Sc., of "oleo-oil” and “neutral lard" used as butter adulter

ants.

TABLE NO. 5.-Melting point of mixtures made in laboratory as indicated. [Tho butter used had a melting point of 330.1 C.; the "olco-oil" of 29°.6 C.; and the "neutral lard"

of 420.4 C.]

From the above it appears that the melting point of a mixture of two or more fats can be readily and accurately calculated from that of its constituents. The agreement, except in No. 1, is within the error of ordinary observation.

Remarks on preceding data.-The mean melting point of the butters examined is 33°.S C., the maximum is 340.7 C., and the minimun 320.6 C. In general terms it may be said that a genuine butter will show a melting point falling within the limits of 330 and 34° C. Of butter adulterants the "neutral lard" has a comparatively high melting point and "oleooil" a low one. Unfortunately for analytical purposes it is easy for the fabricator to make an artificial butter whose melting point is sensibly the same as that of the genuine article. On the other hand it is seen that if a false butter be made of a genuine one and only one of the adulterants in common use, the variation of the melting point from the normal will be sufficiently great to call attention to the falsification.

19330-No. 13———4

EFFECT OF TIME ON MELTING POINT OF THE FAT DISKS.

By some variations in the meiting point of fat disks of different ages my attention was directed to an investigation of the effect of time. The following data will serve to measure the influence of age on the melting point:

In every case except No. 5 in the above table it is seen that the melting point of the disks of butter was raised by standing on water at or dinary temperatures for twenty-four hours.

In one instance, a butter whose melting point was 340.5 C. stood in the form of disks from May 27 until August 3. An attempt was made on this latter date to determine its melting point. At a temperature of 75° C. the disk had not assumed a spherical shape, and the temperature could be carried no higher on account of approaching the boiling point of the alcohol,

Again in every case but one a marked rise in the melting point.

It would appear from the above results that adulterated butters and butter adulterants show a greater rise in melting points when the disks

are a day or more old than pure butter. The analytical data, however, are too meager to permit a definite statement of this kind. Should it prove to be true, it would be a valuable indication in the discrimation between pure and adulterated butters. An examination of the old disks with the microscope did not reveal a crystalline structure, and this change, therefore, must be attributed to a molecular modification or superficial oxidation.

EFFECT OF THE PRELIMINARY HEATING OF THE FAT TO DIFFERENT TEMPERATURES.

à butter fat was melted at a low temperature and allowed to stand until the temperature had fallen to 30° C.; it was still perfectly fluid. The disks were formed by dropping on ice as usual. The melting point obtained was 33° C. The fat was now heated to 50° C. and treated as above; melting point, 330.4 C. The temperature was then raised to 80° C.; melting point, 320.8 C.

The above results, falling within the possible error of observation, show that the temperature to which the fat is subjected before the formation of the disks has no appreciable effect on the point at which the fat particle becomes a sphere.

EFFECT OF SUDDEN RISE OF TEMPERATURE.

A sudden rise of temperature tends to greatly lower the melting point. A fat which showed a melting point of 350.3 C. when determined in the usual way, melted at once into a perfect sphere when dropped into the water-alcohol mixture having a temperature of 29° C. At 28°.5 C. the globule was irregular.

A disk of neutral lard, having by the usual method a melting point of 420.4 C., became at once a sphere when dropped into the water-alcohol at 360.2 C. Below that temperature the spheroidal shape was not symmetrical.

In all cases this phenomenon will appear. It may be suggested, therefore, with strict propriety, whether this may not be regarded as the proper melting point. Since the temperature at which the spheroidal state is assumed can be determined within one or two degrees by a preliminary trial, it would not be difficult to have a series of mixtures of water and alcohol arranged so as to show differences of temperature of 00.5 C. By dropping the disks successively into these mixtures the instantaneous fusing point could be determined with accuracy.

The method set forth in the preceding pages has been proved by 165 determinations to be capable of giving agreeing results. Not only will the numbers obtained by the same observer be concordant, but also those of different analysts. This arises from the fact that the moment of the assumption of the spheroidal state is easily determined even by an unpracticed eye. I have also noticed that in this condition pure butter and oleo are quite transparent, while on the other hand neutral

́rd and adulterated butters are still somewhat opalescent. From this at is seen that the data obtained by the old method of determining the temperature of transparency would differ somewhat from those obtained by the proposed procedure. Since the age of the disk has a great deal to do with its melting point, I suggest that all determinations be made within fifteen minutes to two hours from the making of the disks.

The method can also be extended to such bodies as paraffine and bees-wax. The melting point of a paraffine was found to be

An interesting phenomenon was observed in determining the melting point of the paraffine, which may be made to show, in a lecture experiment, the change of volume which bodies sometimes undergo in passing from a solid to a liquid state. The same mixture of water and alcohol used in the examination of fats, allowed the disk of paraffine to sink to about the same point as the disk of fat. When the temperature rosc, however, to within one or two degrees of the melting point, there was a sudden increase in volume. The pellet of paraffine rapidly rose to the top of the tube. To avoid this and keep the globule within the liquid I made a mixture of water-alcohol and absolute alcohol. With this arrangement the rise of the paraffine was arrested. in the upper third of the tube occupied by the absolute alcohol, where its assumption of the spheroidal state could be readily observed. On placing the tube in a cooling bath the globule of paraffine rapidly sinks as it solidifies The disks of paraffine and bees-wax are quite irregular, but nevertheless suitable for the process. The melting point of the one sample of beeswax examined was found to be 640.2 C.

VISCOSITY.

The speed with which at identical temperatures and pressures different oils flow through an orifice may be used to dintinguish them from each other. For a description of the methods used in viscosimetry I refer to Allen's Com. Organic Analysis. An ingenious and useful apparatus for viscosimetry has been invented by Babcock.2

Babcock has applied his apparatus to the investigation of the viscos ity of butter soaps with promising results."

1 Vol. 2, 2d ed., pp. 194 et seq.

2 Fifth Ann. Rept. Bd. Control N. Y. Exp. Sta., pp. 316 et seq.

3 Ibid., pp. 338 et seq.