ROACH PASTES. 



45 



the carbon bisulphid. Boil for ten minutes. Precipitate out the phos- 

 phate formed with molybdate solution and wash. Dissolve on the 

 (liter with ammonia and determine the phosphorus with magnesia mix- 

 ture in the ordinary manner. 



While the accuracy of the above method is not great, it appears to 

 be of sufficient value for the use to which it is put. 



Microscopic examination. This is made to determine whether wheat, 

 corn, or any other form of starch is present. 



Reducing sugars. A qualitative examination of a water extract of 

 the paste is made with Fehling solution to see if reducing sugars are 

 present. 



Polariscopic readings. Treat a small unweighed quantity of the 

 paste with water and pass the solution through a filter. Clarify with a 

 little lead acetate and pass through another filter. Transfer 45 cc of 

 the solution to a 50 cc flask, make up to the mark with water, mix, 

 transfer to a 200 mm tube, and take a reading. Transfer another 45 cc 

 of the solution to a 50 cc flask, add 5 cc of concentrated hydrochloric 

 acid, mix, invert by heating to 68 C., taking fifteen minutes in so doing, 

 filter, and again take :i reading in a 200 mm tube at practically the same 

 temperature as that of the former reading. If reducing sugars are 

 present and the polariscopic reading is-f- before inversion and after 

 inversion, the presence of molasses is indicated. If reducing sugars 

 are present and the polariscopic reading is -+- before inversion and 

 practically the same + reading after inversion, glucose sirup is indi- 

 cated. If reducing sugars are present and the reading is -f- before 

 inversion and a less + reading after inversion, molasses which has been 

 mixed with glucose may be present. 



ANALYSES AND DISCUSSION. 



Table VIII shows the results obtained by the above methods of 

 analysis on five samples: 



TABLE VIII. Composition of roach pastes. 



Samples 1^)489 and 20490 appear to consist of phosphorus, flour, and 

 molasses. Sample 20491 consists of phosphorus and flour with some 



