Bauhaus-Universität Weimar

Titel:
Handbook for the Physiological Laboratory. Text
Person:
Burdon-Sanderson, John Scott E. Klein Michael Foster T. Lauder Brunton
PURL:
https://digitalesammlungen.uni-weimar.de/viewer/image/lit18583/436/
BY BE. LAUDER BRUNTON. 427 
1st. Its precipitation when boiled and acidulated with nitric 
icid. 
2nd. Its precipitation by acetic acid and ferrocyanide of 
potassium. 
3rd. Its precipitation when boiled with acetic acid and a 
strong solution of neutral salt. 
The student should first try these tests with a solution known 
to contain albumin, so as to become familiar writh them, and 
afterwards with a solution which may or may not contain it. 
1. Put some of the fluid in a test-tube and heat it over a 
spirit-lamp or Bunsen’s burner till it boils. Add a drop or two 
of nitric acid so as to give it a most distinctly acid reaction. 
If a precipitate is formed by boiling and is unchanged by 
the nitric acid, or if one forms after the addition of the acid, 
the fluid contains albumin. 
The acid is added for two reasons, (a) To dissolve any sub¬ 
stance which might be present in the solution, and being pre¬ 
cipitated by boiling might simulate albuminous coagulation. 
Such substances are calcium phosphate which is present in 
human urine, and calcium carbonate in the urine of herbivora. 
As this test is very frequently used for detecting albumin in 
urine, these substances might very easily lead to error. 
Albumin which has been coagulated by heat is not soluble in 
nitric acid, and if the precipitate produced in the fluid by 
boiling disappears on the addition of acid, no albumin is 
present. 
(b) To neutralize alkali which might hinder the albumin from 
being precipitated by boiling. 
Take some solution of albumin in water, add a few drops of 
liquor potassæ and boil. No precipitate occurs. Add one drop 
of dilute nitric acid—any precipitate which forms disappears on 
shaking the tube. Add sufficient to make the fluid very distinctly 
acid, and a permanent coagulum will be produced. The quantity 
of acid added must therefore not be too small, or some albumin 
may remain in the solution. Sometimes, instead of using nitric 
acid, the fluid is kept boiling, and acetic acid added very 
gradually till the fluid is neutral. Unless very great care is 
taken to neutralize the fluid exactly, this method may fail, for if 
an excess of acetic acid be added it will retain the albumin 
solution. If neutralized exactly, the albumin will be precipi¬ 
tated, and may be separated from the fluid by filtration. 
2. Acidulate the fluid strongly with acetic acid, and then add 
several drops of a solution of potassium ferrocyanide. If albumin 
be present, a white flocculent precipitate will occur. 
3. Add acetic acid to the fluid till it is very distinctly acid,
        

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