126 THE ROTARY PROPERTIES OF 



included salt. The percentage of ash in the dried proteid 

 having been previously determined by ignition, the weight of 

 ash- and water-free proteid in 100 cubic centimeters could 

 easily be calculated. The concentration of the proteid solution 

 was varied by diluting it in a graduated flask with the original 

 solvent. 



Acid and Alkaline Solutions. The globulins studied, except 

 when very dry, can be completely dissolved hi dilute acid or 

 alkaline solutions with comparative ease. This simplified 

 very much the preparation of such solutions. The percentage 

 of moisture in the globulin, which was kept in a bottle under 

 fairly constant conditions of temperature and humidity, was 

 carefully determined by drying it at 110 C. Thus, the per- 

 centage of moisture and of ash being known, the amount of 

 water- and ash-free matter in a given weight could be readily 

 found. In making the solutions a few grams of the glob- 

 ulin were weighed out and completely dissolved in the acid or 

 alkali, and the solutions were then made up to the required 

 strength in a graduated flask. 



A few alkaline solutions were also prepared by the addition 

 of a definite volume of 8 per cent potassium hydroxide to a 

 sodium-chloride solution of the globulin. If the alkali is not 

 too weak it can be added to a salt solution in this way without 

 precipitating the globulin. Acids, on the contrary, produce 

 precipitation immediately when added to such a globulin 

 solution. 



The 0.2 per cent sodium-carbonate solution used as a solvent 

 was made in a similar manner to the neutral salt solutions, 

 the sodium carbonate being weighed out and dissolved in dis- 

 tilled water. The other alkalis and acids used as solvents 

 were made up approximately to the requisite strength with 

 distilled water, and their exact strength was afterward deter- 

 mined by titration. 



Apparatus and Methods of Observation. 



The polarimeter observations were made in a large dark room 

 partitioned off in the centre of the building, and a "half- 



