XV.] SOME IMPORTANT ORGANIC SUBSTANCES. IO3 



(c.) A piece of the great pectoral muscle of a pigeon, either fresh or which 

 has been placed in glycerine to render it more transparent, on being pressed 

 between two pieces of glass shows absorption bands of myo-haeiuatin. (Mac- 

 Munn.) Map out their position with the spectroscope. 



LESSON XV. 

 SOME IMPORTANT ORGANIC SUBSTANCES. 



1. Hydrochloride of Glycosamin. The chitinous parts of crabs and lob 

 sters are freed as much as possible from their soft parts," dried, and divided 

 into small pieces, which are decalcified in dilute hydrochloric acid. Gently 

 boil the decalcified parts for 3-4 hours with hydrochloric acid, then evaporate 

 and allow to crystallise. On cooling, a dark brown humus substance and 

 crystals separate out. Filter, dissolve the crystals in water, and re-evap- 

 orate until crystallisation takes place. The hydrochloride of glycosamin 

 (CgHjsNOgHCl) separates in colourless glancing crystals about the size of a 

 pea, which readily reduce Fehling's solution on boiling. They have a some- 

 what sweet taste like sugar. 



2. Nuclein of Yeast. Mix i part of fresh German yeast with 4 parts o f 

 water, allow the deposit to subside. Pour off the turbid fluid from the si;, - 

 deposit of yeast, place the latter in .5 per cent, caustic potash, stir for some 

 time, and filter directly into dilute hydrochloric acid. The deposit is filtered 

 off', washed with dilute hydrochloric acid, and then with alcohol. It is then 

 boiled with alcohol and dried over sulphuric acid. 



(a.) It is an amorphous powder, insoluble in water and dilute acids, but 

 readily soluble in alkalies. 



(b. ) Fuse a little with sodic carbonate and nitrate of potash = a mass with 

 a strongly acid reaction due to phosphoric acid. 



3. Lecithin. 



(O.R 1 

 C -"' LfOH 



Extract the fresh yellow of eggs free from white, with ether, until the latter 

 takes up no more. Distil off the ether, dissolve the residue in petroleum 

 ether, and filter. Extract the filtrate in a separation filter several times with 

 75 per cent, alcohol. Mix the alcohol extracts, let them stand until they 

 become clear, separate any petroleum ether, and filter. The rest of the petro- 

 leum ether is got rid of by distillation, and the residue is exposed for several 

 days to the air in a cool place, whereby a deposit separates. The clear fluid 

 is decanted and filtered. Decolorise it by boiling with animal charcoal, filter 

 and evaporate to a thick syrup at 50-60. Dissolve the syrup in ether and 

 evaporate, and the nearly pure lecithin remains behind (Drechscl). 



1 R = radical of palmitic acid (C 15 H 31 CO), stearic acid (C^H^CO), or oloic 

 acid (0 17 H W CO). 



