102 Profs. A. Gamgee and W. Jones. [May 15, 



5. 25 c.c. of the original solution were correspondingly made 

 distinctly alkaline with ammonia and polar i metrically examined : 



W = M09 grammes; V = 100 c.c.; L = 200 mm.; a = +3 31'. 

 [a] D = +158-7. 



The two above sets of experiments show that determinations of 

 the optical activity of thymus-nucleic acid may be made in a neutral 

 or quasi-neutral fluid, without fear of variation caused by inaccuracy 

 in observing the point of exact neutrality. The following experiments, 

 however, demonstrate that the rotation is markedly changed by the 

 addition to a neutral solution of thy mo-nucleic acid either of a con- 

 siderable amount of acetic acid or of ammonia. 



6. 20 c.c. of the original solution were treated with one-tenth of a 

 c.c. of 20 per cent, acetic acid and the solution was polarimetrically 

 examined : 



W = M09 grammes; V = 100*5 c.c. ; L = 200 mm. ; a= + 3 33'. 

 [a] D = + 160-4. 



7. 10 c.c. of the solution used in 6 were treated with 0'3 c.c. of 

 20 per cent, acetic acid and polarimetrically examined : 



W = 1*109 grammes ; V == 101-5 c.c. ; L = 200 mm. ; a = + 3 36'. 

 [a D ] = +164-7. 



Up to this point we observe an increase in the specific rotation of the 

 nucleic acid. If, however, as in the two following experiments, the 

 amount of acetic acid is increased, the optical rotation undergoes 

 diminution. 



8. 10 c.c. of the original solution were treated with 1 c.c. of 

 20 per cent, acetic acid and then polarimetrically examined : 



W == 1-109 grammes ; V = 110 c.c. ; L = 200 mm. ; a = +2' 29'. 

 [a] D = +123. 



The remarkable influence of solution of ammonia is illustrated 

 by the following observations : 



9. 20 c.c. of the solution which had been used in observation 5 

 were treated with 0'5 c.c. of 10 per cent, solution of ammonia and 

 polarimetrically examined : 



W = 1-109 grammes ; V == 102-5 c.c. ; L = 200 mm. ; a= + 2 40'. 

 [a] D = + 123-4. 



10. The solution used in experiment 9 was treated with an equal 

 volume of 10 per cent, ammonia and the resulting solution examined : 



W = 1-109 grammes; V = 205 c.c. ; L = 200 mm. ; a = + 35'. 

 [a] D = +50-8. 



