Of the following substances, which would react positively with Biuret's, Lugol's, and Benedict's?

1. water 2. starch 3. glucose 4. maltose 5. sucrose 6. fructose 7. galactose 8. albumin 9. hamburger juice 10. onion juice 11. milk 12. potato juice 13. lactose

To determine which substances would react positively with Biuret's reagent, Lugol's reagent, and Benedict's reagent, we need to understand their respective tests and the types of compounds they can detect.

1. Water: Water does not contain any organic molecules and therefore would not react with any of the reagents.

2. Starch: Starch is a complex carbohydrate composed of glucose molecules. It would react positively with Lugol's reagent, producing a dark blue-black color due to the formation of a starch-iodine complex. However, it would not react with Biuret's or Benedict's reagents.

3. Glucose: Glucose is a simple sugar and a monosaccharide. It would react with Benedict's reagent, resulting in a red precipitate, indicating the presence of reducing sugars. However, it would not react with Biuret's or Lugol's reagent.

4. Maltose: Maltose is a disaccharide composed of two glucose molecules. It would also react with Benedict's reagent, producing a red precipitate. However, it would not react with Biuret's or Lugol's reagent.

5. Sucrose: Sucrose is a disaccharide composed of glucose and fructose. It would not react with any of the reagents.

6. Fructose: Fructose is a simple sugar and a monosaccharide. It would react with Benedict's reagent, forming a red precipitate. However, it would not react with Biuret's or Lugol's reagent.

7. Galactose: Galactose is a simple sugar and a monosaccharide. It would also react with Benedict's reagent, resulting in a red precipitate. However, it would not react with Biuret's or Lugol's reagent.

8. Albumin: Albumin is a protein and would react positively with Biuret's reagent, forming a purple color due to the presence of peptide bonds. However, it would not react with Lugol's or Benedict's reagent.

9. Hamburger juice: This is likely to contain proteins and would react positively with Biuret's reagent, turning purple. It would not react with Lugol's or Benedict's reagent.

10. Onion juice: Onion juice may contain various compounds, but it is unlikely to contain substances that would react with any of the reagents mentioned.

11. Milk: Milk contains a variety of compounds including proteins and lactose (a disaccharide), so it would react positively with both Biuret's reagent (purple color) and Benedict's reagent (red precipitate). However, it would not react with Lugol's reagent.

12. Potato juice: Potato juice contains starch, which would react positively with Lugol's reagent, forming a dark blue-black color. It would not react with Biuret's or Benedict's reagent.

13. Lactose: Lactose is a disaccharide composed of glucose and galactose. It would react with Benedict's reagent, producing a red precipitate. However, it would not react with Biuret's or Lugol's reagent.

In summary, the substances that would react positively with the reagents mentioned are:

- Lugol's reagent (detects starch): Starch and potato juice.
- Biuret's reagent (detects proteins): Albumin, hamburger juice, and milk.
- Benedict's reagent (detects reducing sugars): Glucose, maltose, fructose, galactose, hamburger juice, milk, and lactose.