634 FOODS AND FOOD ADULTERANTS. 



I therefore ask your cooperation in this work in the examination of one hundred 

 and seventy-five samples of saccharine products, as follows : 



Fifty samples of molasses: Polarization before and after inversion; sucrose; re- 

 ducing sugar before inversion ; qualitative test for tin ; water; ash. 

 Fifty samples of liquid honey: Polarization before and after inversion; sucrose; 

 reducing sugar before inversion ; water; ash; fermentation; polarization of 

 residue after fermentation. 



Fifty samples low-grade sugars: Polarization; water; ash. 



Twenty-five samples of cheap confections (candies, etc.) : Sucrose before and after 

 inversion ; reducing sugars ; matters insoluble in water ; water, ash, and col- 

 oring matters (mineral or non-mineral). Get a few highly colored samples. 

 You will bo authorized to purchase the samples in open market and without indi- 

 cating the purpose for which they are to be used. 



The molasses should be purchased in packages of about 1 quart, the honey and 

 sugar in about 1 pound lots. 



The sugar when purchased is to be immediately put in air-tight packages, so as to 

 avoid loss of moisture. 



In every case the name of the dealer from whom the purchase is made is to be 

 entered, together with the name of the firm manufacturing the product, and labels or 

 descriptions on the package, and such other descriptions as will give any information 

 concerning the sample. 



The itemized bill for the samples is to be sent to the Department, and you will be 

 compensated therefor. 



It is not required that the whole of the analytical work is to be performed by you 

 personally, but it must be under your personal direction and responsibility. Full 

 directions for conducting the analyses will be sent. The work is to be finished and 

 reported to me by March 1, 1891. 

 Respectfully, 



H. W. WILEY, 



Chemist. 



DIRECTIONS FOR ANALYSIS OF SUGARS, HONEYS, AND CONFECTIONS. 



It was thought proper to leave to each analysist as large a degree of independent 

 action as possible in carrying on the work, and therefore only a general outline of the 

 method of conducting the work was supplied. 



The reading of the polariscope employed is to be given for the 200 mm and 100 mm 

 tubes, with the sample of sugar sent, weighing 26.048 g. in the air, and making up to 

 100 cc in a flask graduated at that mark to hold 100 g distilled water at 17.5 for instru- 

 ments with a Ventzke scale, or 16.19 g sugar weighed in air in flask graduated at 100 

 cc, with 100 g water at 4 for Laurent scale. These readings of the instrument are 

 to accompany the analytical data. 



The direct polarizations are to be made in the usual way, using lead subacetate for 

 clarifying the solutions, neutralizing with acetic acid, and rejecting first part of the 

 nitrate. Bone black is only to be used in extreme cases. If dried at 100 to 105 it 

 can be added directly to the solution after the volume is completed. If moist, it must 

 be placed on the filter paper and the first half of the filtrate rejected. 



For inversion 50 cc of the normal solution are to be heated for ten minutes to 6d 

 with 5 cc strong hydrochloric acid, cooled quickly to constant temperature, and polar- 

 ized. The percentage of sucrose is calculated from Clerget's formula. The polari/a- 

 tion should be made at the same temperature as the direct polarization of the same 

 sample. 



Reducing sugars. The alkaline copper solution should be set by the sample of (prac- 

 tically) pure sugar sent. The operations should be conducted on solutions containing 

 about 1 per cent of reducing sugar, and under precisely similar conditions as those 

 used i 11 setting the copper solution. 



