20 Keratin Sulfur and Cystin Sulfur [March, 



V. The second portion of the same fluid was evaporated to dry- 

 ness, and the sulfur-content determined, after fusion with potas- 

 sium hydroxid and potassium nitrate. The result was : 0.5 172 gm. of 

 barium sulfate (0.07105 gm. of sulfur). Hence, the sulfur-content 

 of 700 c.c. was 0.4974 gm. It is clear that a much greater amount 

 of the sulfur (92.3 percent) is contained in the filtrate from the 

 oxy-proto sulfonic acid in the form of some organic combination, 

 and only a small part {y.y percent) is present in the Solution as 

 sulfuric acid. 



For the second experiment, 10.2085 gm. of dry fat-free human 

 hair were digested with 800 c.c. of 2 percent sol. of potassium per- 

 manganate and allowed to stand for 3-4 days, until the fluid was 

 perfectly clear. This was then filtered and, of the filtrate, two por- 

 tions of 100 c.c. were taken. 



VI. The first portion was treated as in determination IV, with 

 the difference, that this time the sulfur-content of the oxy-proto 

 sulfonic acid precipitate was also determined. The filtrate and 

 wash-water were treated with barium chlorid after the removal of 

 the oxy-proto sulfonic acid, and yielded 0.4230 gm. of barium sul- 

 fate (0.00581 1 gm. of sulfur). Hence, in 800 c.c, 0.0465 gm. of 

 sulfur was present as sulfuric acid. 



VII. After the fusion of the oxy-proto sulfonic acid precipi- 

 tates, with a mixture of potassium hydroxid and potassium nitrate, 

 0.0117 gm. of barium sulfate (0.00161 gm. of sulfur) was found. 

 The sulfur in the oxy-proto sulfonic acid amounted, therefore, to 

 0.0129 gm. 



VIII. The second portion was treated as in determination V. 

 After fusion, 0.4694 gm. of barium sulfate (0.06449 gm. of sulfur) 

 was obtained. Hence, 0.5159 gm. of sulfur was present in 800 c.c. 



From these experiments it follows, unquestionably, that the 

 greater part of the sulfur occurs, after oxidation with permanga- 

 nate, as water-soluble organic substance. Of the total sulfur-con- 

 tent in the dissolved oxidation products (0.5159 gm. of sulfur) 

 there were found: 9 percent as sulfuric acid, 2.5 percent as oxy- 

 proto sulfonic acid, and 88.5 percent as a water-soluble organic 

 substance. 



This water-soluble substance gives a precipitate with lead ace- 



