Xerofoam gauze and glycerin-soaked cotton were placed in the umbilicus.

Xerofoam = not a noun or pronoun
gauze = noun
and = not a noun
glycerin = noun
soaked = not a noun
cotton = noun
were = not a noun or pronoun
placed = not a noun or pronoun
in = not a noun or pronoun
the = not a noun or pronoun
ubilicus = noun

In this construction, "glycerin-soaked" is an adjective.

The others are correct.

Can you please explain why?

Glycerin-soaked is hyphenated -- making it one word. It's used as an adjective modifying cotton. It tells what kind of cotton is being used.

When the word "glycerin" stands alone, it is indeed a noun.

Example: Glycerine is a colorless, odorless, syrupy, sweet liquid.

Xerofoam, gauze, glycerin-soaked cotton, and umbilicus are all nouns in the given sentence.

To identify nouns, we can look for words that refer to people, places, things, or ideas. In this sentence, "Xerofoam," "gauze," "glycerin," "cotton," and "umbilicus" are all objects or substances that can be seen or touched, making them nouns.

Here's a breakdown of the nouns in the sentence:

1. Xerofoam - a product or material (noun)
2. Gauze - a thin, woven fabric used for dressings or bandages (noun)
3. Glycerin - a viscous liquid used in various applications (noun)
4. Cotton - a soft, fluffy fiber used to make textiles (noun)
5. Umbilicus - the medical term for the navel or belly button (noun)

Other words in the sentence, such as "and," "were," "placed," "in," and "the," are not nouns or pronouns. They serve as conjunctions, verbs, or prepositions, which have different grammatical functions.