Introduction to the study of organic chemistry : a text-book for students in the universitites and technical schools / by John Wade.

  • Wade, John.
Date:
1898
Catalogue details

Licence: Public Domain Mark

Credit: Introduction to the study of organic chemistry : a text-book for students in the universitites and technical schools / by John Wade. Source: Wellcome Collection.

    448/490 (page 426)
    brown product with, boiling caustic soda. Reduces alkaline copper tartrate on warming (2 grams copper sulphate and 10 grams Rochelle salt in 25 c.c. water ; when completely dissolved add solution of 3 grams caustic soda in 15 c.c. water). Reduces copper-acetic solution on boiling for 2 min. (see milk-sugar). Reduces bismuth hydroxide (bismuth nitrate and caustic soda). Crystalline osazone (chap. xxxi.). [Estimation of Glucose.—Fehliug’s solution : Copper and alkaline tartrate solutions mixed just before use, as mixed solution does not keep well. Solu- tion A: 17'32 grams recrystallised copper sulphate (exactly weighed) dis- solved in 150 c.c. water, and cold solution made up to exactly 250 c.c. Solution B : 35 grams caustic soda and 90 grams recrystallised Rochelle salt dissolved in 150 c.c. water, and cold solution made up to exactly 250 c.c. To estimate sugar in solution, place 5 c.c. A, and 5 c.c. B in small flask, with 40 c.c. water and piece of glass to check bumping, and boil. Then run in sugar soln. from burette 2 c.c. at a time, until colour of supernatant liquid is just faintly yellow after ppt. has settled (sheet of white paper behind flask). 1 mol. glucose reduces 5 mols. copper sulphate, so that 10 c.c. of mixed soln.=50 milligrams of glucose. This is therefore the quantity in the amount of solution required to decolourise the copper. If the strength of the sugar solution is less than 1 gram or more than 1 gram per 100 c.c., re- sults are only approximate, and estimation must be repeated on concentrated or diluted solution. If Fehling’s solution old, prove by inverting 0'475 gram cane sugar as above, and making up to 100 c.c. ; 10 c.c. of this should just decolourize 10 c.c. Fehling.] [Milk Sugar.—Curdle 100 c.c. milk at 30° with a drop of hydrochloric acid. Evaporate filtered and neutralised whey to syrup, and cover up and leave to crystallise.] Qualitative Tests for Uillc Sugar (p. 175).—Gritty and only slightly sweet. Sparingly and only slowly soluble in cold water. Does not blacken when heated with cone, sulphuric acid. Does not colour with caustic soda. Re- duces alkaline copper tartrate, but does not reduce copper-acetic solution on boiling for 2 minutes (1 gram copper acetate, 25 c.c. water, 20 drops'; B.P. acetic acid). Forms osazone characteristic crystals. [Estimation of Milk Sugar.—As with glucose, but 10 c.c. Fehliug=0'0G7 gram lactose.] Fermentation of Glucose.—10 grams glucose in 100 c.c. water, in a flask with delivery tube. Add a little yeast (teaspoonful), and keep at 30°. Note carbon dioxide, and when action is finished, distil and test for alcohol. CHAPTER XXIX Starch.—Separate starch from flour as indicated. Qualitative Tests for Starch (p. 180).—Insoluble in cold, soluble in hot water ; blue iodide, with iodine iu potassium iodide. Decolourised by heat, colour returns on cooling; hydrolysis to glucose, which reduces copper. \_Estimation of Starch.—Heat 1 gram with 100 c.c. water and 10 drops cone, sulphuric acid in open flask on a w.-b. until drop of solution (cooled) ceases to give blue with iodine (30-60 min.). Then neutralise with soda and proceed as with glucose. 10 c.c. mixed Fehling = 0'0455 gram starch.] Hydrolysis of Starch.—2 grams rubbed to cream with 10 c.c. water and made up to 200 c.c. Boil portion with few drops of dil. sulphuric acid for few minutes, and neutralise ; test with copper and caustic soda tests. Dextrin.—Moisten 5 grams starch with dil. sulphuric acid, and heat iu test-tube in sulphuric acid bath at 200° for an hour. Brown product now soluble in water ; reduces copper, and gives either red or no colour with iodine. Cellulose.—Add excess of cone, ammonia to soln. of 2 grams copper sul- phate in 20 c.c. water. Add filter paper to this as long as it disappears. Filter and add excess of dilute sulphuric acid.