chrome alum: meaning, definition, pronunciation and examples
Low / TechnicalScientific, Historical/Industrial Technical
Quick answer
What does “chrome alum” mean?
A specific double sulfate compound of chromium and potassium (or ammonium) with the chemical formula KCr(SO4)2·12H2O or (NH4)Cr(SO4)2·12H2O, appearing as violet crystals.
Audio
Pronunciation
Definition
Meaning and Definition
A specific double sulfate compound of chromium and potassium (or ammonium) with the chemical formula KCr(SO4)2·12H2O or (NH4)Cr(SO4)2·12H2O, appearing as violet crystals.
Used historically in dyeing and tanning as a mordant due to its chromium content; sometimes used in photography and as an astringent. The term is also used to distinguish this specific chromium-containing alum from other alums like potassium alum.
Dialectal Variation
British vs American Usage
Differences
No significant difference in term usage; spelling follows regional norms for 'sulfate' (UK: sulphate).
Connotations
Equally technical in both regions.
Frequency
Equally low frequency in both dialects, confined to chemistry, historical industrial texts, and specialized crafting contexts.
Grammar
How to Use “chrome alum” in a Sentence
[to] use chrome alum [as a mordant][to] prepare a solution [of chrome alum]chrome alum [is/was] employed [in dyeing]Vocabulary
Collocations
Examples
Examples of “chrome alum” in a Sentence
noun
British English
- The dyer obtained some chrome alum to use as a mordant for the wool.
- Old photographic manuals sometimes mention chrome alum for hardening emulsions.
American English
- The chemistry set included a sample of chrome alum.
- Chrome alum's violet crystals are quite distinctive under the microscope.
Usage
Meaning in Context
Business
Rare; might appear in supply catalogs for historical re-enactment crafts or specialty chemical suppliers.
Academic
Used in chemistry textbooks and papers discussing coordination compounds, mordants, or historical industrial processes.
Everyday
Virtually never used.
Technical
Primary domain: chemistry, historical dyeing/tanning manuals, photography (as a hardening agent for gelatin).
Vocabulary
Synonyms of “chrome alum”
Neutral
Weak
Vocabulary
Antonyms of “chrome alum”
Watch out
Common Mistakes When Using “chrome alum”
- Confusing it with 'potassium alum' or 'aluminum'. Misspelling as 'chromalum'. Using 'alum' generically when 'chrome alum' is specifically meant.
FAQ
Frequently Asked Questions
No. Common 'alum' is usually potassium aluminium sulfate. Chrome alum is potassium chromium sulfate, containing chromium instead of aluminium.
It typically forms dark violet or purple crystals.
Its main historical uses were as a mordant in dyeing textiles, in leather tanning, and as a hardening agent in early photographic gelatin processes.
Chromium(III) compounds like chrome alum are less toxic than chromium(VI), but all chemicals should be handled with appropriate safety precautions. It can be a skin irritant.
A specific double sulfate compound of chromium and potassium (or ammonium) with the chemical formula KCr(SO4)2·12H2O or (NH4)Cr(SO4)2·12H2O, appearing as violet crystals.
Chrome alum is usually scientific, historical/industrial technical in register.
Chrome alum: in British English it is pronounced /ˌkrəʊm ˈæləm/, and in American English it is pronounced /ˌkroʊm ˈæləm/. Tap the audio buttons above to hear it.
Learning
Memory Aids
Mnemonic
Think of 'chrome' as in chromium, the metal that gives the compound its violet colour, and 'alum' as the class of double sulfate salts it belongs to.
Conceptual Metaphor
A specialised tool in a colourist's or tanner's toolkit, often conceptualised as a 'fixative' or 'bridge' that binds dye to fibre.
Practice
Quiz
What is the primary metal ion in chrome alum?