426 Conversion of Starch into Sugar. [Drc. 
dough before it was washed, there remained 5th of the filtered 
liquid. Therefore when I give the result here 1 increase the last 
by one ninth. 
I poured barytes water into the filtered liquid as long as any pre- 
cipitate fell. This precipitate, after being heated to redness, 
weighed 6°7 grammes, and was sulphate of barytes. A small 
quantity of it passed through the filter, and was afterwards found 
in the ashes of the starch sugar. Now this sulphate of barytes 
_contains all the sulphuric acid which was employed in experiment. 
The solution thus freed from sulphuric acid was reduced to the 
consistency of a thick syrup, and then left in a state of repose. It 
furnished a yellowish sugar, which, after long exposure to the open 
air in a temperature of 52°, and while the hair hygrometer stood at 
75°, weighed 96°89 grammes. Such was the quantity of sugar 
obtained from 96 grammes of starch. So that 100 grammes starch 
will yield 100°93 grammes of sugar, supposing both dried at the 
temperature of the atmosphere ; but this result must be brought to 
the temperature of boiling water before we can put much confi- 
dence in it. 
100 grammes of the starch with which these experiments were 
made, being exposed for six hours to a heat of 212°, lost 13°4 
grammes of water ; and when burnt left 0°16 of ashes. 
On the other hand 100 grammes of solid starch sugar treated in 
the same way, lost 4°93 of water, and left 0°75 of ashes, most of 
which was sulphate of barytes that had passed through the filter. 
If according to these results we reduce the starch and its sugar to 
a boiling heat, and subtract from them the ashes, we find that 100 
parts of starch will form 110-14 parts of sugar. 
This sugar, when dissolved in half its weight of water, formed a 
syrup, which might be mixed with alcohol of 36° of Baume’s areo- 
meter in any proportion, without the precipitation of any gum. 
Hence gum does not constitute a portion of starch sugar, as some 
have believed, except when the process has not been continued 
long enough, or when the starch itself has been scorched, in 
which case the starch sugar will be lighter than the starch from 
which it was obtained. 
As starch boiled in water with sulphuric acid, and thereby 
changed into sugar, increases in weight without uniting with any 
sulphuric acid or gas, or without forming any gas, we are under the 
necessity of ascribing the change solely to the fixation of water, 
Hence we must conclude, that starch sugar is nothing else than a 
combination of starch with water in a solid state. 
The sulphuric acid and other acids appear to act no other part 
in the process, than to promote the fluidity of the aqueous solu- 
tion of the starch, and thereby facilitate its combination with 
water.* 
* The attempts of Kirchof and others, to convert flour or potatoes directly 
into sugar by this process have entirely failed, —GILBERT. 
