OF ARTS AND SCIENCES. 



Ill 



good a quality as possible. The arrowroot, which is the most exten- 

 sively adulterated of the three, was tested both by means of the vapor 

 of iodine and the microscope, so that no doubt might exist of its being 

 a pure article. 



" The determinations were made in the following manner. The dif- 

 ferent specimens were dried in watch-glasses at a temperature of 100° 

 C. (212° F.), and were all dried for the water determinations in their 

 market condition, with the exception of maccaroni, which seemed likely 

 to offer so much resistance to the escape of moisture, that it was pul- 

 verized previously to drying. They were then all pulverized, thorough- 

 ly dried at the same temperature (100° C), and the determinations of 

 carbon, hydrogen, and nitrogen made. The combustions for carbon 

 and hydrogen were effected in the usual manner with oxide of copper, 

 the portion of oxide of copper at the extremity of the tube being in- 

 timately mixed with very finely pulverized chlorate of potassa. The 

 nitrogen was determined as ammonio-chloride of platinum by ignition 

 with soda-lime, according to the method of Varrentrapp and Will. 

 As the amount of nitrogen was exceedingly small in most of the 

 specimens, it was supposed that the chloride of ammonium produced 

 in the hydrochloric acid employed, by the absorption of ammonia from 

 the air, might produce a perceptible effect upon the results of the 

 analyses. Coincident determinations were therefore made with the 

 hydrochloric acid in every analysis, by evaporating portions of acid 

 and bichloride of platinum equal to those actually employed in deter- 

 mining the results of the combustions, collecting the precipitate on a 

 weighed filter as usual, washing with alcohol, &c. It was found, how- 

 ever, in every case, that the filter lost more from washing with alcohol 

 than it gained by the precipitate ; it was therefore necessary to make a 

 small addition, generally about 0.0014 grm. to the amount of ammo- 

 nio-chloride of platinum obtained from the combustion. In making 

 a statement of the results, the nitrogen was taken as the basis of the 

 calculation ; carbon, hydrogen, oxygen, and sulphur were distributed to 

 it according to the proportions indicated by the -formulae of nitrogenous 

 bodies. Albumen and gluten agree with each other so nearly in con- 

 stitution, as given in the analyses of Scheerer (Ann. der Chem. und 

 Pharjn., XL. 38), of Mulder, and of Killing {Ann. der Chem. und 

 Pharm., LVIII. 310), that a single formula has been taken, namely, 

 that of Mulder ; — 



