EXPERIMENT STATION BULLETINS. 369 



The bone was first sifted through a soil sieve of the following sized 

 meshes: 2.0, 1.0, 0.5, 0.25 m. m. in the clear. The gxade passed by the 

 1.0 m. m. mesh but retained by the 0.5 m. m. mesh was used, the other 

 being discarded after screening. The following method was employed for 

 removing the dry blood and waste soluble matter from the bone. 



1. About 300 grams of the screened bone meal were steamed for two 

 hours in one liter of a 0.5% salt solution using distilled water and chemi- 

 cally pure sodium chloride. 



2. Cold tap water was then added, the contents of the vessel stirred 

 thoroughly and allowed to settle when the top scum and the suspended 

 blootl particles were poured off from the surface. This washing was 

 repeated from six to eight times, or until the bone was clean and 

 white and free from all dark colored particles. 



3. It was then transferred to a porcelain evaporating dish and dried 

 over a water bath with frequent stirring when it was ready for use. 



ROCK PHOSPHATE. 



The rock phosphrJe was obtained in a finely ground condition from 

 tlie South Carolina Mining and Manufacturing Co., Nash\ille, Tenn., 

 and a chemical analysis showed it to contain : — 



Insoluble Material 17.22% 



CaO 35.10% 



ALO3 5.56% 



• Fe'O, 4.78% 



PA 26.72%, 



ANALYTICAL METHODS. 



On the specified dates, the flasks were taken to the chemical labora- 

 tory, the solutions filtered and made up to the volume of 500 c. c, 

 from which duplicate samples of 200 c. c. each were taken for analysis. 



The filtering of the solutions was accomplished at first with no little 

 difticulty. Owing to the sliminess of many of the solutions, due to bacter- 

 ial growths, filtering through paper was practically an impossibility, 

 and it was only after the following scheme was devised, that this part of 

 the operation was performed satisfactorily. A four-inch Buchner filter 

 was used with a thick pad of long fiber asbestos as the filtering medium. 

 Through this the solution passed quite rapidly, at the same retaining 

 the finest particles of the bone and phosphate rock. 



The digestion of the solutions was conducted as follows: Ten cubic 

 centimeters of concentrated sulphuric acid were added to each flask, and 

 after the excess of water had l^een driven off by boiling, small quantities 

 of concentrated nitric acid were added from time to time until the solu- 

 tions were colorless. 



The phosphoric acid was then determined according to the gravimetric 

 method adopted by the Association of Official Agricultural Chemists. 

 .47 



