These are sold to the spice grinders under the name of “P. D.” pepper. Pepper adulterants and pepper mixtures,—P. D., pepper dust; H. P. D., hot pepper dust; W. P. D., white pepper dust—consist of such products as the grinder has at hand or can obtain at the lowest price, the mixer requiring only that the colors shall be such as are suitable for his trade. In London, the olive stones are much used, put up in colors of both black and white. Pepper mixtures are sold under the name of “Poivrette or Pepperette.” Their natural color is pale buff, much resembling the middle layer of the pepper berry when ground, and they cannot be distinguished from the pepper by the eye, even with the use of a hand lens, when mixed with a powdered pepper, but with the aid of the microscope with one-sixth or one-eighth objective, it is seen that they consist of pale, dense, lignous cells, being entire and marked with linear air spaces; some are torn and indistinct. Other substances examined showed finely ground clay and brick dust. The presence of pepper husks and charcoal is generally known by the immensely increased proportion of black particles in the field, as appears in [Fig. 43], opposite page 25, Chap. III.

The true pepper powder, and one in which rice starch is present, is given in [Fig. 21] and in [Fig. 42], which also gives us an idea of the size of the pepper starch, which is very small as compared with any other kind of starch. Much authority might be quoted on the adulterations of pepper, but enough has been written to give the reader an idea of its vastness. I will next endeavor to give the method of examining peppers microscopically. First, the sieve examination of those particles left upon a forty to sixty-mesh sieve is of value. This examination will frequently reveal the nature of the adulterant or the too large portion of pepper husk.

Next, by the aid of a good dissecting microscope, fifteen to thirty power, the frequency of the occurrence of the coarse particles, after a little experience, will not be difficult to sort out, and the presence of sand or a notable excess of P. D. may be detected and estimated. Backgrounds of white and black with reflected light and afterwards transmitted light may be used in the manner so conveniently afforded by Zeiss’s stand made for this purpose. A portion of the powdered pepper or the separated coarse particles should also be treated with a chloral-hydrate solution for twenty-four hours, to render it more transparent for examination with higher powers, and in the meantime a part of the coarse particles collected from the sieve may be examined under a one and one-half inch objective and then crushed and re-examined, using both plain and polarized light. In this way husky matter may be distinguished and foreign starches rejected. Polarized light is then the means of bringing out more plainly the starches, the proportion of which iodine will reveal. Due allowance should be made for the smaller granules of pepper starch and all optically active tissue, such as the fibers and sclerenchyma or stone cells, which are found in olive stones and cocoanut shells. The chloral-hydrate preparation should now be examined, much of which disappears, and the starch is found much swollen. The structure of the pepper itself has already been explained and is supposed to be so well understood that it cannot be confused with the foreign matter, as the husky matter present is rendered so much clearer that its identification and differentiation are much easier. Experience with half a dozen samples of cheap, in comparison with a pure, pepper will soon teach one the best means of making out what has been briefly described.

It has been found most valuable to digest about a gram of pepper with nitric acid, specific gravity 1.1, and chlorate of potash for several hours, or until the color is bleached, when it is then possible to distinguish the denser cellular structure more easily than in any other way. This is particularly true of the stone cells, which make up the larger part of the cocoanut shells and ground olive stones, especially when polarized light is used. Care should be taken not to confuse the stone cells of the pepper husk with those of olive stones or other adulterants. Charcoal at the same time remains unbleached. The analyst will find many variations in the samples met with and should always be on guard for something new.

Chemical composition of black pepper.—The analysis of the pure ground pepper shows the amount of water to be between 8 and 10 per cent., but, of course, it varies with surrounding conditions. The ash in black peppers does not exceed from 4-10 to 7-10 per cent., and in white, 4-10 per cent.; it is fair to believe that anything above 5 per cent. for black and 2 per cent. for white is suspicious. The volatile oil, to which pepper owes its flavor, varies in black pepper from 1.69 to .70, and in white 1.26 to .57 are found, but this determination is not of great value as a means of detecting adulterations.

Piperine, which is a neutral crystalline substance, and resin, to which the pepper owes its pungency, of which it yields about two per cent. in its composition, are similar to oil of turpentine as well in specific gravity as in the boiling point. These substances furnish a most valuable check on the purity of both white and black pepper. Pepper contains from 7.90 to 7.24 per cent. of these substances, showing a great constancy in amount, and on addition of adulterants, this is plainly affected, which seems better than a determination of pure piperine, which is difficult and causes much loss. It has also proved impossible to make determinations of piperine by the combustion, or K. Jeldahl, methods by application of Stutzer’s copper-hydrate process, the percentage of nitrogen being so small, 4.912 in piperine, as to make the error very large when converting the former to the latter, the necessary factor being 20.36.

The determination of starch or its equivalent in reducing sugars has been looked into with care, and a preliminary extraction with alcohol and water is necessary to obtain results which are fairly constant, which determination shows black pepper to contain from 34 to 38 per cent. of starch, or 42 to 47 per cent. of substances of reducing sugar equivalent, calculated on dry ash free substance. White pepper contains in the same way from 40 to 43 per cent. starch and gives from 50 to 55 per cent. of reducing sugar equivalent on dry ash free substance.

The crude fiber in black pepper does not vary far from 10 per cent., but in the white pepper is much reduced, depending to a certain extent on the perfection of the decortication. Four to 8 per cent. are probably fair limits, and this determination is quite necessary in revealing the presence of foreign woody or fibrous matter.

Albuminoids do not vary widely, 10 per cent. being the average, with extremes of 7.69 and 11.50. The addition of nitrogenous seeds, of course, increases the amount, and of fibrous or woody matter diminishes it. We have the following result as a standard:

Water,8.0 to 11.0
Ash,2.75 to 5.0
Volatile Oil,.50 to 1.75
Pepperine and Resin,7.0 to 8.0
Starch,32.0 to 38.0
Crude Fiber,8.0 to 11.0
Albuminoids,7.0 to 12.0