IMPROVED APPARATUS FOR DETECTING SULPHURED GRAIN. 1 



By George H. Baston, Assistant in Grain Standardization. 



The apparatus - commonly in use for detecting sulphured grain 

 consists of an Erlenmeyer flask of 500 c. c. capacity, fitted with a 

 cork stopper and a delivery tube. 



The chief objection to this apparatus is that it is almost impossible 

 to make a cork connection perfectly tight, and it is also very hard 

 to keep clean. The escape of the gas around the stopper was the 

 first difficulty that the writer tried to overcome. Rubber stoppers 

 are not practicable for this purpose on account of the sulphur which 

 they contain. A hollow, ground-glass stopper with a glass delivery 

 tube attached was substituted for the cork connections. The hollow 

 in the center of the stopper should be filled with cotton, which acts 

 as a filter, thereby preventing the dirt and dust from being carried 

 over with the gas. The dimensions of the apparatus are shown in 

 figure 1. 



The method used for detecting sulphured grain is as follows : 



Place 100 grams of the grain to be examined, together with 10 grams 

 of zinc, mossy or granular, chemically pure and free from sulphur, 

 in a 500 c. c. flask. Pour into the flask enough diluted hydrochloric 

 acid (1 part of acid to 4 parts of distilled water, by volume) to just 

 cover the grain. Close the flask with the ground-glass connection 

 and place the end of the glass delivery tube in a test tube containing 

 a 2 per cent solution of lead acetate (2 grams of chemically pure lead 

 acetate in 98 c. c, of distilled water) which has just been filtered. 

 The test tube should be only about three-fourths full of the lead- 

 acetate solution, in order to prevent spilling when the gas begins to 

 pass over. The delivery tube should extend to within about 1 inch 

 of the bottom of the test tube. Figure 1 shows how the apparatus 

 should be adjusted. 



In the case of unbleached grain, the gas liberated from the zinc 

 and hydrochloric acid is hydrogen; with grain which has been 

 bleached with sulphur, the gas liberated is hydrogen sulphid, the 



i Issued Feb. 1,1913. 



2 The method for the detection of sulphured gram is described in detail in Circular 40, Bureau of Plant 

 Industry, U. S. Department of Agriculture, entitled "A simple method of detecting sulphured barley 

 and oats," by W. P. Carroll, Assistant in Grain Standardization. 



[Cir. Ill] 23 



