SERUM ENZYMES 541 



1. The Gold Solution: 



AuCl a Merck's yellow crystals hermetically sealed in brown 



glass ampules 1 gram 



Water triply distilled, up to lOOc. c. 



This stock solution is kept well stoppered in dark glass bottles 

 .away from any bright light. 



2. The Alkaline Solution: 



Merck's Blue Label Potassium Carbonate (desiccated) 2 grams 



Water triply distilled, up to ' 100 c. c. 



3. The Reducing Agents : 



a. Formaldehyde, Merck's 40 per cent stock solution, highest 



purity 1 c. c. 



Water triply distilled, up to 40 c. c. 



b. Oxalic acid, Merck's Blue Label, Crystals 1 gram 



Water triply distilled, up to 100 c. c. 



Solutions ~No. 2 and No. 3 must be made up immediately prior 

 to use. 



4. Bichromate cleaner for glassware: 



Potassium Bichromate, powdered 200 grams 



Water, distilled, up to 1500 c. c. 



Sulphuric Acid cone 500 c. c. 



The potassium bichromate should be well dissolved before the 

 sulphuric acid is added. If this solution is reserved for cleaning 

 glassware only, it can be used repeatedly. 



Great attention must be paid to the cleaning of glassware. They 

 boil their Jena beakers in Ivory soap solution, then brush under hot 

 tap water. After being rinsed for five minutes, hot bichromate and 

 sulphuric acid is added for half an hour. The beaker is then 

 emptied and washed in running water for five minutes, rinsed with 

 distilled water and then in triply distilled water. Similar methods 

 are used with other glassware. The chief errors are insufficient 

 brushing, failure to get all bichromate out, and allowing beakers to 

 dry in air before using. 



In obtaining the distilled water, they first take ordinary distilled 

 water which they then re-distil from Jena flasks. They wash out 

 the collecting flasks with the first 200 c. c. of the second distillate, 

 then collect and re-distil in the same way, again rinsing with the 

 first 100 c. c. of the second distillate. After all these steps have 

 been performed the rest is more or less simple. A beaker rinsed out 

 with triply distilled water is filled to the liter mark and the tem- 

 perature raised to 50 C. gradually, then the gas is turned on full 

 and when the temperature has reached 60 C. 10 c.c. of the 1 per cent. 



