370 
On the application of the Spectrum-microscope to the 
Chemistry of Beer. 
In studying the colouring matters in beer it is, in the first 
place, desirable to understand those met with in the various 
substances used in brewing ; but it is unnecessary to take into 
consideration colours insoluble in water. 
When malt is digested in hot water an orange-yellow 
colouring matter is extracted, but the solution contains so 
much sugar and gum as to interfere with the necessary 
experiments. It should, therefore, be evaporated to the con- 
sistency of syrup, alcohol added by degrees, and the pre- 
cipitated gum and sugar well stirred up, so that as much 
colouring matter as possible maybe dissolved. After standing 
till quite clear this solution on evaporation yields a pale orange- 
yellow syrup, which when dissolved in water or alcohol gives 
a spectrum without any decided characters. Ammonia makes 
it a deeper and brighter yellow, and the same change occurs 
when it is dissolved in sulphuric acid. In all these experi- 
ments a mixture of equal volumes of the concentrated acid 
and water should be used, for if much stronger it chars 
vegetable substances, and if weaker it does not act well with 
the reagents added to it. When dissolved in this the colour 
of malt is made much darker by the addition of nitric acid or 
chlorate of potash, but an excess of the latter makes it rapidly 
fade to a pale yellow ; whilst hypochlorite of soda in small 
quantity makes it somewhat more orange, and more makes it 
a very pale yellow. The characteristic test is hypochlorite of 
soda, added to an aqueous or alcoholic solution, in which a 
little citric acid has been dissolved. The addition of a 
suitable quantity of the hypochlorite turns the aqueous solu- 
tion to a pink flesh-colour, becoming deeper ; but it is not 
clear, and on standing a copious pink flocculent deposit sub- 
sides. When seen to the greatest advantage, the spectrum 
is 4 . - - 8 , . 10 - - 11 — , without any decided narrow absorp- 
tion-bands. If, however, the colour was dissolved in alcohol, 
the solution remains clear; there is a well-marked band at 
the yellow end of the green, which at first is 4f, and, as the 
colour becomes deeper, is more distinct, and rises to 5. The 
flesh-coloured deposit from the solution in water is easily dis- 
solved by alcohol, and gives the same spectrum ; and these 
facts are so unique that this colouring matter could be easily 
recognised in complicated mixtures. It certainly does not 
occur in barley, and must, therefore, be formed in the pro- 
cess of malting. Water extracts from barley a brown colour 
