GENERAL BIOLOGY 



Then add 8 drops of dextrose solution and boil again. Result? 

 This is the "dextrose test." Copper sulphate (Cu So 4 in an alkaline 

 solution is "reduced" to yellow cuprous hydroxide (Cu OH) or 

 to red cuprous oxide (Cu 2 O) when boiled with a reducing sugar. 



Test your urine for sugar in this way. 



2. DISACCHARIDS (Sucrose, maltose, lactose) can be split into 

 monosaccharids by hydrolysis. 



a. CANE SUGAR (Sucrose). Take a few drops of i% solu- 

 tion and test with Benedict's or Fehling's Fluid. Is it a reducing 

 sugar ? 



b. HYDROLYSIS OF CANE SUGAR. Boil some of the i % solution 

 with a few drops of hydrochloric acid. Cool, neutralize, and apply 

 Benedict's test. Is a reducing sugar present? 



3. POLYSACCHARIDS. Native starch, a. Mount a scraping of 

 potato in water and examine under microscope. Study and draw 

 structure of starch grains. Run a drop of iodine solution under 

 cover. What happens? 



b. Grind a little commercial starch in a mortar and shake with 

 cold water. Filter and test nitrate with iodine. Explain result. 



c. Test solubility in boiling water. Note character of resulting 

 solution. Dilute and add a drop or two of iodine solution. What 

 results, and why? 



d. Cellulose (plant cell-walls). Cotton fiber is almost pure 

 cellulose. Note insolubility in water and alcohol. Is it insoluble in 

 acids ? Alkalies ? Does it react with iodine ? Treat with 40 per cent 

 sulphuric acid and then add iodine. What results? Treat with 

 Schultze's chlor-zinc-iodide. 3 Explain results. This is known as 

 the "cellulose test." 



1 Benedict Fluid: Copper sulphate, 17.3 grams; Sodium or potassium 

 citrate, 173.0 grams; Sodium carbonate, 200 grams; Distilled water to 

 make 1000 cc. 



2 Fehling's Fluid: (i) Copper sulphate, 34.65 grams; Distilled water to 

 make 500 cc. ; (2) Potassium hydroxide, 125.0 grams ; Rochelle salt, I73-O 

 grams; Distilled water to make 500 cc. (3) Mix equal parts of (i) and (2) 

 when needed for use. 



3 Schultze's Chlor-zinc-iodide is made as follows: (i) Dissolve no 

 grams of zinc in 300 cc. hydrochloric acid and evaporate to 150 cc. ; (2) 

 Dissolve 12 grams of potassium iodide in as little water as possible and 

 add 0.15 grams iodine; (3) Mix (i) and (2), and filter if necessary. 



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