544 CHEMISTRY OF THE PROTEIDS CHAP. 



were able to exclude the presence of both glucosamin and also 

 glycuronic acid, which latter Schmiedeberg has assumed to be present. 

 The hexosamin-acid gives Ehrlich's reaction with p-dimethyl-amino- 

 benzaldehyde (see p. 10), which is believed to be a test for the 

 mono- or di-acetate of glucosamin. 



The percentage composition of chondro-sulphuric is 



C 35-28 H 4-68 N 3'15 S 6*33 50'56 (Morner). 



C 37-1 H 4-83 N 271 S 5'5 50-14 (Schmiedeberg). 



Some other preparations of Schmiedeberg showed slight deviations. 



Chondro-sulphuric acid has a strongly acid reaction, and forms 

 with metals neutral salts which, as a rule, are readily soluble. 

 Schmiedeberg prepared amorphous copper-, iron-, and potash salts, as 

 well as a copper-oxide salt. In water the acid is readily soluble, and if 

 sufficiently concentrated is of a gum-like consistence. It is precipi- 

 tated by stannous chloride, basic lead acetate, mercurous nitrate, 

 ferric chloride, and uranium nitrate, but not by other metals, nor by 

 any acid, or by the alkaloidal reagents. By acetic acid it is, however, 

 precipitated if the acid be largely in excess, and by alcohol if salts 

 are present. It does not reduce, but keeps copper oxide and other 

 metallic oxides in solution by forming soluble salts. Its watery 

 solutions are laevo-rotatory. 



With albuminous substances, for example with gelatine, chondro- 

 sulphuric acid forms insoluble salts, which behave like nucleic acids, 

 for they become hydrolytically dissociated in the absence of an excess 

 of acid. The salts of chondro-sulphuric acid, however, do not precipi- 

 tate albumins, and therefore the mixture of sodium or potassium 

 chondro-sulphate and gelatine, which one obtains by digesting cartilage 

 with pepsin, or by boiling cartilage in a Papin-pot, is only precipitated 

 if the chondro-sulphuric acid is liberated by the addition of other acids ; 

 mineral acids in excess re-dissolve the precipitate. This reaction is 

 also of importance in connection with the mucoid found in the urine 

 (see below). The greater part of chondro-sulphuric acid is a con- 

 stituent of chondro-mucoid, but a small amount, according to Morner 

 and Schmiedeberg, occurs in cartilage either in the free state or as an 

 alkali -salt. To demonstrate the presence of combined and free 

 chondro-sulphuric acids, Morner proceeds as follows : The tissues are 

 extracted with caustic potash, the extract is neutralised ; the chondro- 

 sulphuric acid is precipitated with alcohol and dissolved in water. 

 This watery solution must show the following reactions : 



1. Give a precipitate with gelatine and acetic acid. 



2. Give a precipitate with glacial acetic acid. 



