80 Messrs Morreli and Bellars, Some Compounds 



substances which are very hygroscopic. The glucose, fructose, 

 maltose compounds are composed of three molecules of the sugar and 

 two of guanidine, but those obtained from galactose and rhamnose 

 seem to contain an equal number of molecules of sugar and base. 

 In several cases there is combined alcohol, which is not removed 

 in a vacuum ; Lobry de Brtiyn found that the rhamnosamine 

 crystallised out with a molecule of methyl alcohol. The com- 

 pounds react strongly alkaline in aqueous solutions, and their 

 optical activity is generally much lower than that of the parent 

 sugar ; moreover it diminishes slowly with time until a constant 

 value is obtained. The rotation angle of the glucose compound 

 in water becomes in time negative, and that of fructose slowly 

 falls to a constant value, which is of the same sign as that of the 

 parent sugar. The change of sign in the rotation angle of the 

 glucose compound may point to a slow transformation of glucose 

 into fructose as observed by Lobry de Brtiyn. We have not yet 

 examined . the aqueous solution of the glucose compound for 

 mannose and fructose. Dilute acids decompose the compounds at 

 the ordinary temperature, but the concentration of the acid must 

 be considered, as will be seen from the following experiments : 

 172 grs. galactose compounds on treatment with lOc.c. N.HC1 



N 

 required 50"71 c.c. Y7\ c - C - NaOH for neutralisation. Percentage of 



guanidine = 16*86. 



1-2501 grs. dissolved in 100 c.c. water and treated with 12 - 5 c.c. 

 N.HC1 required 101-6 c.c. N/10 NaOH. % guanidine = 11-04. 



2089 grs. rhamnose compound on treatment with 125 c.c. 



N 

 N.HC1 required 73'55 c.c. ^t^ NaOH. Percentage of guanidine 



= 14-57. 



0'9498 grs. rhamnose compound, dissolved in 25 c.c. water, on 

 treatment with 12*5 c.c. N.HC1 required 1105 c.c. N/10 NaOH. 

 Percentage of guanidine = 8'82. 



The compounds of glucose and maltose with guanidine are 

 decomposed completely by the dilutest hydrochloric acid. 



Picric acid precipitates guanidine picrate from aqueous solu- 

 tions of compounds of guanidine with glucose, fructose, galactose, 

 and rhamnose, but the yield of picrate depends on the concentration 

 of the solution in the case of the fructose and rhamnose com- 

 pounds. The influence of concentration of acid and time on the 

 decomposition of aqueous solutions of these sugar-compounds is 

 still under investigation. Their optical activity is generally much 

 lower than that of the parent sugar, and diminishes slowly until 

 a constant value is obtained. The specific rotation of the glucose 

 compound is [a^] = 29'0°, which sinks in 6 days to [a^,] = — 6 - 2° ; 

 for the galactose compound [od] = 52'9°, which becomes in 8 days 



