DESCRIPTIOX OF THE APPARATUS. 1 



o 



used with safety if the necessary precautions are taken to prevent the 

 temperature running- too hi«>:h : however, an oil with a flash i)oint as 

 low as 175° C. in an open cup is not to he reconunended for general 

 use. An oil with a flash point of from "200° to 205° C. (open cup) 

 and a viscosity of 10 or 15 at 20° C. (Engler) is more desirahle. 

 Oils of this character are found among many grades of lubricatinff 

 oils, especially those known as " engine oils," and can be purchased 

 in barrel lots for about 12^ or 15 cents a gallon. 



As the moisture is liberated from the grain the foaming of the oil 

 will be quite pronounced, and the flask nuist be sufficiently large to 

 prevent the foaming oil from being carried over into the condenser 

 tube. The foaming can be greatly reduced by the addition of from 

 15 to 20 per cent of paraffin, but this is usually tnuiecessary. 



QUANTITY REQUIRED. 



The quantity of the oil in the distillation flask admits of a w'ide 

 variation, it being only necessary to have such a quantity of oil that 

 all of the grain used for the test will be immersed. One hundred 

 grams of corn require approximately 100 cubic centimeters of oil, 

 ■while if only 50 grams of grain are used the quantity of oil can be 

 reduced. The quantity of oil used, however, is not an important 

 factor, inasmuch as the greater part of it can be recovered b}^ empty- 

 ing the contents of the flask into a colander at the close of the test 

 and allowing the oil to drain off. The oil so recovered can be used 

 again with equalh" as good results as with fresh oil. But even if the 

 oil is not used a second time, 1 gallon, costing 12^ or 15 cents, is suf- 

 ficient for forty tests. 



DESCRIPTION OF THE APPARATUS. 



In devising the apparatus for making moisture determinations in 

 accordance with the method outlined in these pages, the principal 

 aim has been to secure an apparatus suitable for laboratories engaged 

 in determining the percentage of water in samples of commercial 

 grain. The following description and the accompanying illustra- 

 tions (figs. 3, 4, 5, 6, 7, and 8) show^ the detailed construction of the 

 apparatus. 



THE EVAPORATING CHAMBER. 



For the want of a better term the name '' evaporating chamber " 

 has been applied to that part of the apparatus in which the sam- 

 ples of corn immersed in the oil are heated. (See figs. 4 and 5.) The 

 evaporating chamber {B) is made of a good quality of gah'anized 

 iron and is divided into six compartments, as shown in figure 4. 



99 



