178 DIRECTIONS FOR LABORATORY WORK. [BOOK II. 



SECT. 16. DIRECTIONS FOR LABORATORY WORK CONNECTED 

 WITH GASTRIC DIGESTION. 



1. Determination of the Specific Gravity of Gastric Juice. 



Follow method described in Vol. I., p. 174. 



2. Determination of Total Solids and fixed Mineral Matter. 



Follow method described in Vol. L, p. 177. 



3. Preparation of an Artificial Gastric Juice. 

 Follow methods 1 and 4 described at pp. 82 and 83. 



4. Determination of the degree of Acidity of the Gastric Juice, 

 or of the filtered Contents of the Stomach. 



It is usual to express the acidity of the gastric juice as equivalent 

 to n grm. of HC1 in 100 or 1000 parts. 



In order to make the determination there are required : 



(1) A burette say of 30 or 50 c.c., divided into tenths of a cubic 

 centimetre. 



(2) A pipette which delivers 10 cubic centimetres ; it is con- 

 venient to have a second which delivers 5 c.c. 



(3) Beakers. 



(4) A decinormal solution of sodium hydrate. 



(5) A neutral solution of litmus (see Vol. I., p. 176). 



Process. The burette is filled to the top of the graduation with 

 the decinormal soda solution. 10 c.c. of the gastric juice of which 

 the acidity is to be determined are placed in a beaker, and 1 c.c. 

 of the perfectly neutral solution of litmus added. 



The solution of caustic soda is then allowed to flow in until the 

 red litmus is changed to blue. The volume of the soda solution 

 used is then determined. If n be the number of cubic centimetres 

 of decinormal soda used, and x the amount of acid expressed as HC1 

 in 1 litre of the gastric juice, 



x = ?ixO 00365 x 100. 



5. Determination of the presence of free Hydrochloric Acid, by 



Colour Tests. 



Test separate small quantities of the gastric juice or of the fluid 

 filtered from the contents of the stomach with the various reagents 

 described in the text (see page 92, et seq.}, but especially with 

 alcoholic solution of OO Tropaeolin (see p. 94). 



