104 Dr. Prout on the ultimate Composition 



two experiments, 12*5 parts, and on being analysed in this 

 state gave Carbon 42*8 



Water 57'2 



which very nearly coincides with what by calculation it ought 

 to have given, on the supposition that the loss of weight was 

 owing to the escape of water, a circumstance indeed of which 

 there could have been little doubt. Starch however in this 

 state still retains water, a portion of which may be separated 

 by subjecting it to higher temperatures. Thus, after having 

 been exposed as above for twenty-four hours to the tempera- 

 ture of 212°. on being further submitted to a temperature be- 

 tween 300° and 350° for six hours longer, it lost 2*3 per cent, 

 more, and analysed in this state gave very nearly 



Carbon 44 



Water 56 



It had now acquired a slight yellow colour, and seemed to 

 have suffered some change in its properties ; hence, this is pro- 

 bably nearly the utmost quantity of water that starch is ca- 

 pable of parting with, short of decomposition. 



Arrow root. — This is another variety of the amylaceous prin- 

 ciple, of which, like sugar, there seems to be a great variety. 

 The specimen on which the following experiments were made 

 was remarkably fine, and free from adventitious matters. It 

 had been kept in the same drawer with the starch before men- 

 tioned, and under precisely similar circumstances of the at- 

 mosphere was found to consist of (abstracting foreign matters) 



Carbon 36*4 



Water 63*6. 



One hundred parts, in the above state, exposed for twenty 

 hours to a temperature between 200° and 212°, lost fifteen 

 parts. Hence its composition, when thus dried, was very 

 nearly the same as that of wheat starch similarly exsiccated ; 

 or it consisted of Carbon 42-8 



Water 57*2. 



On being subjected to the full temperature of 212° for six 

 hours longer it lost 3'2 per cent, more, and was then reduced 

 to a state similar to that of starch dried between 300° and 

 350°, or it consisted very nearly of 



Carbon 44*4 



Water 55'6 



When subjected to the temperature of 300° and 350° for six 

 hours longer, it lost 1 '38 per cent, more of its weight, but be- 

 came of a deeper yellow colour than starch similarly exposed, 

 and consequently showed greater marks of decomposition. 

 Hence, this form of the amylaceous principle, like the sugar 

 of honey before mentioned, seems to part with the whole of 



the 



