Paul Haas and T. G-. Hill 361 



cold or with dilute sodium carbonate followed by nitration and dialysis 

 also failed to have the desired effect. 



Subsequently it was found that the amount of sulphate which is 

 precipitated from an aqueous solution of the extract is very much 

 greater after hydrolysis with dilute acids than before such hydrolysis; 

 this observation may account for the difficulty experienced in removing 

 the ash constituents by dialysis. 



Nitrogen Content. 



Both the weed and the product obtained from it by extraction with 

 water give positive reactions for proteins with concentrated nitric acid 

 and with Millon's reagent, but the glyoxylic acid reaction for trypto- 

 phan is not given by either. 



Estimations of nitrogen in the dried weed and the various extracts 

 gave the following figures: 



A. Dried plant 1-93 % 



B. Scale carrageen : 



(i) Cold water extract ... ... ... -99 „ 



(ii) Hot water extract of residue from (i) 1-09 „ 



(iii) Direct hot water extract ... ... -82 „ 



(iv) Residue from (iii) ... ... ... 4-82 „ 



The figures given by previous authors for the nitrogen content of the 

 plant are: Jolles 2-08 per cent., Fliickiger and Obermaier 1 percent., and 

 Thorpe 1 1-5 per cent. 



Hydrolysis. 



The use of carrageen as a food naturally leads to the examination of 

 its behaviour under the action of various hydrolytic agents. The work 

 of others has shown that the water extract of carrageen is a poly- 

 saccharide which is converted into various sugars by the action of strong 

 mineral acids 2 , but from this it does not follow that carrageen can be 

 hydrolysed by the agents it normally encounters in the human or in the 

 animal system. For this reason many experiments were carried out with 

 solutions of scale carrageen in order to find out the effect of relatively 

 weak hydrolytic agents. In all cases the presence of reducing sugars 

 after the reaction was taken as a positive result: controls always were 

 employed and due precaution taken to guard against bacterial action. 

 Since scale carrageen gives a slight acid reaction, its solution was ren- 

 dered neutral or alkaline when appropriate. 



1 Thorpe's Dictionary of Applied Chemistry. 



2 Our observations on this aspect of the subject are reserved for a future occasion. 

 Ann. Biol, vn 24 



