70 P. C. Ray — Chemical Exammatton of [No, 1, 



wliich it was contained was immersed in ice-cold water to completely 

 solidify the separated fatty acids. The glycerin solution was then 

 filtered off and made up to 250c. c. of which 20 c. c. were each time oxidised 

 to oxalic acid. Tlie oxalic acid was thrown down by calcium acetate. 

 The precipitate of CaO was dissolved in HCl, further acidified with 

 H2SO4, and titrated with N/10 KMnO^,. The streugth of the permanga- 

 nate solution was ascertained each time by titration against re-crystallised 

 oxalic acid and sometimes against ferrous ammonic sulphate. 



7" 5 c. c. N/10 KMn04 were used up by the oxalic acid solution. 



1 c. c. N/iO KMn04 = 00063 gm. O = 0'0046 gm. glycerin; hence 

 amount of glycerin in 20 c. c. sol, 



=0-0046 X 7-5 gm. 

 .'. Total glycerin in 250 c. c, 



= (00046 X 7-5) x~gm. 



= 0'431 gm. 

 Per cent, of glycerin in the oil = 4'98. 



But the N/10 KMnOi= 0-0061 gm. O instead of 0-0063 gm. O. 

 Per cent, of glycerin in the oil = 4-82. 

 2. 8'48 gm. oil were saponified just as above. The glycerin solution 

 made up to 250 c. c, of which 50 c. c. were oxidised to oxalic acid. 



The oxalate solution was divided into two equal portions, one-half 

 (a) ( = 25 c. c, glyc. sol.) was acidified with HgSO^, heated to boiling 

 and titrated, the other half (b) was treated with Ca Ac, and the pre- 

 cipitated CaO dissolved in dilute HgSO^ and then titrated with 



^ KMnO,. 



N 

 (a) Requii-ed 17-0 c. c. ~ KMuOj 



(h) „ lo'O „ „ 



1 c. c. ^ KMnO4=00046 gm. glyc. 



15c. c. ^ ., =00046x 15 gm. glyc. = 0-069 gm, glyc, 



.-. 250c. c. glyc. solution contains 0'69 gm. glycerin. 

 Per cent, of glycerin in the oil =8" 14. 

 Experience has shewn that the oxalate solution if titrated direct, 

 after addition of H2SO4, gives the result too high. Precipitation of the 



e£Eecting saponification by aqueous alkali, and thus completely avoiding the source 

 of error in question." Jour. Soc. Chein. Ind. V, 70; also Sutton's Volumetric 

 Analysis, 6th ed. p. 345. 



