MICROSCOPICAL EXAMIXA'I'ION. 



When tlie maima is observed uiulei- a lens, slender, bright, 

 radiating crystals are observed, principally in the hollows of the 

 mass.^ When examined under the miscroscope, they are found to 

 polarize in bright colours, principally blue, green, and purple. 

 The crystals are rhombic prisms with brachypinacoid faces; 

 these crystals extinguish parallel to the principal axis. When 

 the mannite is removed, purified, and crystallized fronT water, 

 transparent crystals are formed which do not polarize in colours, 

 or only occasionally, and then very faintly. 



CHEMICAL EXAMINATION. 



If the manna be boiled in dilute alcohol, and filtered hot, the 

 filtriite, on becoming cold, consolidates into a crystalline mass. 

 it tins be stirred with alcohol, filtered, and well washed with 

 alcohol on tlie filter, the dark-coloured substances contained in 

 the manna will be removed, and also a portion of the mannite. 

 -Ir the residue be now dried, then dissolved in water, and crystal- 

 lized from that medium, the crystals may be purified by two or 

 three crystallizations from water and alcohol. When thus purified, 

 the crystalline substance only reduces alkaline copper-solution to 

 tlie very slightest degree on boiling, although the manna itself 

 reduces Fehling's solution very readily. 



The manna melts at 1.58-9° C, while the purified mannite 

 iiieltsat 160-1° C. A specimen of mannite fresldy prepared from 

 ^'raxmus-m&mvA melted, at the 

 the same conditions, at 1C1° C, 



same time and under precisely 



ESTDIATION OF GLUCOSE. 



T\v( 



.j„^ '''-' gi'ams of the manna \\'ere dissolved in water, made up to 

 -'J'J cc. It required 174 cc. to reduce 10 cc. of Fehlin"'s 



The manna 



required 174 cc. to reduce 10 

 popper-solution (10 cc. =0-0-5 gramme glucose) 

 therefore contains 2-87 per cent, of a glucose. 



J. wo grams of the same manna were dissolved in water, boiled 

 with dilute hydrochloric acid for half an hour, and then made up 

 o ..UU cc. This solution required 148 cc. to reduce 10 cc. of 

 J^ehlmgs solution = 3-38 per cent, of 

 consequently we have 3-38 - 

 ■sugai's other than a glucose. 



ULTIMATE ANALYSIS 



jlucose after inversion, 



2-87 = --^l per cent, of 



a suffar or 



of 

 and 



The 



THE CRYSTALLINE 

 THE MANNA. 



SUBSTANCE FOUND IN 



^ substance was purified as much as possible n-itJiont the aid 

 animal charcoal. It was repeatedly crystallised from water 

 , °"ol. and was eventually obtained almost white. The 

 rystals are anhydrous. Analvses made 20th July, 1892. 



