§ 23 EXTRACTION WITH SPIRIT. 241 



of good pepsin to toe taken for every 2. grams of finely powdered 

 substance. Starch, if present in large quantily, might with 

 advantage be previously converted into maltose and dextrin by 

 boiling, cooling to 40°, and digesting for four hours at that 

 temperature, after adding 0-005 gram of active diastase. 



§ 234. ExtmdUm with SpirU. — Some of the albuminoids in- 

 soluble in water attract our attention by their solubility in spirit, 

 as, for instance, those known as glutmfibrin, gliadm (or vegetable 

 gelatine), and mucedin. In seeds only have these three substances 

 been detected with certainty ; they rermaiii undissolved when the 

 material containing them is treated with water, or, at most, the 

 mucedin alone is partially taken into solution. They would be 

 removed, however, by the dilute alkali used for the extraction of 

 the glutencasein (§ 226), and it is advisable therefore, in looking 

 for these substances, to treat the material with spirit previously 

 to extracting the glutenoase'in with alkali. Part, however, of the 

 glutenfibrin and a little gliadin would be left undissolved, and would 

 be subsequently found with the casein (§ 226). The spirit should 

 be used cold, and should be of a strength of about 60 to 80 per 

 cent. The maceration must extend over a considerable period, 

 and the spirit be renewed several times. The united extracts are 

 distilled until the strength of the spirit is reduced to 40 to 60 per 

 cent, (not less). On cooling, a clear slimy mass separates, con- 

 sisting principally of glutenfibrin mixed with a few flocks of gluten- 

 casein and possibly fat (which is, however, better removed by 

 petroleum spirit before treating with alcohol). If the majority of 

 the spirit is distilled off from the clear liquor a second precipitate 

 will form, consisting principally of gUadiai and mucediia, and a 

 further quantity of the same two substances (impure) can be ob- 

 tained by neutralizing the filtrate with a h'ttle potash and con- 

 centrating. 



All these precipitates are triturated with absolute al(»>hol until 

 th^ become hard and solid. Fat, if present, is removed by 

 treattnent with ether. 



We are as yet unacquamted with any method of separating the 

 glutenfibrin, gliadin, or mucedin for quantitative determination. 

 We must therefore conient ourselves with making a total estima- 



Th« spirit dissolves a little ghtUnfibrin, which can subsequently he precipi- 

 tated by ether. 



16 



