342 



As the air-dried gum had become quite smoky and dirty in appearance, 

 although it was quite colourless when first precipitated, an effort was made to 

 determine the cause. It was again dissolved in water, but the solution was tlien 

 (luite turbid and evidently contained some insolubli' substance, and this was 

 readily removed by agitating the aqueous solution with alumina cream. The 

 filtrate was perfectly clear, bright, colourless, and on testing a solution of con- 

 siderable strength it was found to be inactive to light. When again precipitated 

 by alcohol and dried (spread on glass as before^, it did not become dark coloured, 

 but remained perfectly clear and transparent, thus showing that no fresh alteration 

 of the manganese salt had taken place. 



The purified gum had all the properties of gum arabic, and ga\'e all the 

 reactions with reagents necessarv for that substance. It was odourless and 

 tasteless, had marked adhesive properties, and would make an excellent commercial 

 gum. It contained a minute trace of a reducing sugar. 



The alumina cream when filtered off was dark coloured, and wlien fused 

 with sodium carbonate and potassium nitrate in the usual wav gave a marked 

 reaction for manganese. A manganese bead was also readily obtained with bora.x. 

 The ash of the first precipitated gum also gave a reaction for manganese, while 

 that of the purified gum did not. The presence of a soluble form of manganese 

 in the latex of this tree was thus demonstrated, and also that it formed the higher 

 oxide on drying in the air. Further information will be found in the article 

 dealing with the presence of manganese in the Australian Coniferae. 



The amount of moisture in tlie purified air-dried gum was 15-5 per cent., 

 and the amount of ash was 2-g per cent. This consisted principally of the car- 

 bonates of lime and magnesia. 



In the preparation of mucic acid, 2 grams of the gum were heated with 

 nitric acid on the water bath until the formation of the acid was complete. Half 

 the amount of water was then added and stood on one side for twentv-four liouis, 

 when the oxalic acid was removed by aleohol. The murir arid formed wns 2 ; per 

 cent., calculated on the air-dried gum. 



The sugar formed b\' hydrolysis was jirepaicd by boiling the gmn in a 

 dilute solution of sulphuric acid for several hours, and remo\-ing the excess of acid 

 by barium carbonate. The filtratr- was tpiite clear and almost colourless, was 

 dextro-rotatory, and it strongh' reduced I'ehling's solution. W hen evaporated 

 down it did not crystallise, but gave reactions which indicated the presence of 

 arabinosc. When boiled uitli plilorogluciiiol in li\-drochloiie acid the reaction 

 was similar to that given by arabinosc sujjplied 1)\ Kalilbaum. i'lie osa/one was 

 formed, but not readily, and although it was somew hat dark rolonred, \'e| it 

 melterl at about 155-160° C. 



