376 Dr. Prout on the ultimate composition 
Wheat Starch. The most perfect form of the amylaceous 
principle is undoubtedly that derived from wheat. This has 
been analysed by different chemists with very different results. 
MM. Gay Lussac and Thenard state that they found it to 
contain as much as 43*55 per cent, of carbon ; while Dr. Ure 
informs us that he only found 38-55 per cent. The following 
observations will sufficiently explain these differences. 
A very fine specimen of wheat starch, which had been 
prepared expressly at my desire without the addition of the 
colouring matter commonly added to the starch of commerce, 
and which had been kept in a dry situation for many months, 
was found, in the ordinary columnar form in which it usually 
occurs, (abstracting foreign matters) to consist of 
Carbon 37-5 
Water 62-5. 
One hundred parts of the same specimen reduced to a state 
of fine powder, and subjected to a temperature between 200° 
and 212 0 , for the space of 20 hours,* lost, in a mean of 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 
* 1 have reason to believe from other experiments that six or eight hours, or even 
less, of steady exposure to the boiling temperature, will sometimes reduce both 
starch and arrow root, and even gum, to this state of desiccation. 
