334 APPLIED IMMUNOLOGY 



neck of the ampoule (A) containing salvarsan (usually 0.6 

 gramme) is nicked with the small file accompanying the 

 commercial package and the neck easily broken. The con- 

 tent is emptied into the mixing cylinder and the substance en- 

 tirely dissolved by shaking, producing a clear light-yellowish 

 solution of a strongly acid reaction. In order to fit this 

 solution for human administration it must be neutralized. 

 Accordingly 1.14? cubic centimetres or approximately 2S 

 minims of a freshly prepared fifteen per cent, solution of 

 purified sodium hydroxide (C) are added. For this purpose 

 a medicine dropper (D) is convenient. The following table, 

 dependent upon the quantity of salvarsan utilized, may be of 

 service : 



Salvarsan 16 per cent. Solution of Sodium Hydroxide 



0.6 gramme requires 1.14 c.c. or approximately 23 to 24 minims. 



The addition of the caustic soda, which should be in one 

 quantity and not added slowly drop by drop, produces a 

 heavy whitish yellow precipitate, redissolved in excess on 

 shaking; if necessary another drop or two of the caustic soda 

 solution may be added. At this juncture the solution should 

 be neutral and perfectly clear, resuming its original light 

 yellowish coloration. It is advisable now to add just one more 

 drop of the soda solution, which will render the solution very 

 faintly alkaline. Slight turbidity or cloudiness of the solu- 

 tion is an indication that insufficient sodium hydroxide has 

 been added. If in doubt the reaction should be tested with 

 litmus paper (L) and the neutrality, weak alkalinity or 

 acidity of the solution definitely determined. If decidedly 

 alkaline, a drop or two of the dilute hydrochloric acid (H) 



