1815.) Conversion of Starch into Sugar. 425 
important remarks. But hitherto nobody has explained what alte- 
rations in its composition the starch undergoes in this process, 
though this would throw considerable light upon vegetation, and 
would elucidate the change of starch into sugar in the buds of 
ts. Professor de la Rive of Geneva, in a paper published in 
the 49th volume of the Bibliotheque Britannique, has shown that 
in Kirchoff’s process no gas is evolved, that the alteration of 
the starch goes on in close vessels without the access of air, 
and that the sulphuric acid is neither decomposed nor united 
to the starch as a constituent. M. Vogel in Paris has made 
the same observations, and has likewise found that long boil- 
ing in pure water does not convert the starch into sugar. Hence 
he concludes, conformably to the well known action of sulphuric 
acid, that even in this case it acts by uniting together a portion of the 
oxygen and hydrogen of the starch and converting them into water. 
In order to elucidate these points, I have endeavoured to deter- 
mine whether the sugar formed from starch by this action of sul- 
phuric acid has a smaller weight than the stareh from which it was 
formed. For this purpose I put into a silver vessel 400 grammes of 
distilled water. I then mixed it with 2-4 grammes of sulphuric 
acid, made it boil moderately on a charcoal fire, and put into it in 
different portions 100 grammes of starch, previously mixed with 
200 grammes of water. During this addition the liquid was con- 
stantly stirred with a spatula, to prevent the starch from being 
burat or becoming brown, which would have diminished its weight 
and rendered the results doubtful. In half an hour the mixture 
was brought from the state of dough to a complete solution.* I 
now put it intoa capsule with a long neck, washed with 200 
grammes of water, the clammy matter left by the starch on the 
silver vessel, dissolved it, put the whole into the capsule, and kept 
it for 42 hours over an Argand’s lamp in a heat never exceedin 
199°. I now weighed the solution, filtered it,-and weighed like- 
wise the white dough which remained behind upon the filter, and 
which may be considered as a portion of starch, which from the 
adhesion of its parts escaped the action of the sulphuric acid. 
This dough being repeatedly washed and dried in the open air, 
weighed 4 grammes, and when examined by means of water, acids, 
and alkalies, exhibited all the properties of starch. We must 
therefore subtract these 4 from the 100 grammes of, starch em- 
ployed in the experiment. Upon the filter, and in this starch- 
* If it be allowed to cool at this time it becomes again partly thick, and when 
filtered leaves upon the filter a considerable quantity of starch still unaltered, 
while the solution passes readily and quite clear, through the paper, When this 
solution is concentrated and mixed with alcohol, there falls down a transparent 
dry colourless matter, not altered by exposure to the air; which, from its solu. 
bility in water, insolubility in alcohol, antl its clamminess when dissolved in a 
little water, is similar to gum. Barytes water, when poured into the solution, 
occasions no precipitate, as barytes and sulphuric acid form a triple compound 
with gummy bodies, which is usually soluble in water, Is this gummy body simi- 
lar in all its properties or not, to the brownish body obtained by roasting starch ? 
