“231.  That on and after July 1, eighteen hundred and ninety-one, and until July 1, nineteen hundred and five, there shall be paid, from any moneys in the Treasury not otherwise appropriated, under the provisions of section three thousand six hundred and eighty-nine of the Revised Statutes, to the producer of sugar testing not less than ninety degrees by the polariscope, from beets, sorghum, or sugar cane grown within the United States, or from maple sap produced within the United States, a bounty of two cents per pound; and upon such sugar testing less than ninety degrees by the polariscope, and not less than eighty degrees, a bounty of one and three-fourth cents per pound, under such rules and regulations as the Commissioner of Internal Revenue, with the approval of the Secretary of the Treasury, shall prescribe.”

It is the opinion of this Commission that the expression “testing ... degrees by the polariscope,” used with reference to sugar in the act, is to be considered as meaning the percentage of pure sucrose the sugar contains, as ascertained by polarimetric estimation.

It is evident that a high degree of accuracy is necessary in the examination of sugars by the Bureau of Internal Revenue, under the provisions of this act, inasmuch as the difference of one-tenth of one per cent. in the amount of sucrose contained in a sugar may, if it is on the border line of 80 deg., decide whether the producer is entitled to a bounty of 13/4 cents per pound (an amount nearly equivalent to the market value of such sugar) or to no bounty whatever.  It is desirable, therefore, that the highest possible degree of accuracy should be secured in the work, for while many sugars will doubtless vary far enough from either of the two standard percentages fixed upon in the act, viz., 80 deg. and 90 deg., to admit of a wide margin of error without material consequences, yet a considerable proportion will approximate to them so closely that a difference of a few tenths of a degree in the polarization will change the classification of the sugar.

A very high degree of accuracy may be obtained in the optical estimation of sugars, if the proper conditions are observed.  Such conditions are (1) accurately graded and adjusted instruments, weights, flasks, tubes, etc.; (2) skilled and practiced observers; (3) a proper arrangement of the laboratories in which the work is performed; and (4) a close adherence to the most approved methods of manipulation.

On the other hand, if due observance is not paid to these conditions, the sources of error are numerous, and inaccurate results inevitable.

We will endeavor to point out in this report the best means of meeting the proper conditions for obtaining the highest degree of accuracy consistent with fairly rapid work.  It would be manifestly impossible to observe so great a refinement of accuracy in this work as would be employed in exact scientific research.