ferricyanic acid
C2Technical / Scientific
Definition
Meaning
A chemical compound with the formula H₃[Fe(CN)₆], the hypothetical parent acid of ferricyanides.
A term for the unstable, strongly acidic compound derived from hexacyanoferrate(III) ion. In practice, it is not isolated as a pure substance but is referenced in the context of its salts (ferricyanides), such as potassium ferricyanide, which are important in analytical chemistry and as oxidizing agents.
Linguistics
Semantic Notes
This is a highly specialized chemical term. The word 'acid' in the name denotes its theoretical classification rather than a commonly handled substance. It is almost exclusively encountered in technical literature discussing coordination chemistry or redox reactions.
Dialectal Variation
British vs American Usage
Differences
No significant differences in usage, spelling, or pronunciation. Both variants use the same International Union of Pure and Applied Chemistry (IUPAC) nomenclature.
Connotations
None beyond its strict scientific definition.
Frequency
Extremely low frequency in general language, occurring only in advanced chemistry contexts in both regions.
Vocabulary
Collocations
Grammar
Valency Patterns
[Ferricyanic acid] is used as a precursor for...The oxidation state of iron in [ferricyanic acid] is +3.Salts derived from [ferricyanic acid] are...Vocabulary
Synonyms
Neutral
Weak
Vocabulary
Antonyms
Usage
Context Usage
Business
Not used.
Academic
Used in advanced chemistry textbooks and research papers discussing coordination compounds or redox chemistry.
Everyday
Virtually never used.
Technical
The primary context. Used in chemical synthesis, analytical method descriptions, and material science papers.
Examples
By Part of Speech
adjective
British English
- The ferricyanic acid compound was theorised in the 19th century.
American English
- The ferricyanic acid group is key to the reaction mechanism.
Examples
By CEFR Level
- Ferricyanic acid is an important concept in understanding certain chemical salts.
- Although ferricyanic acid itself is unstable, its potassium salt is a well-characterised reagent used in blueprint paper and as an oxidant.
Learning
Memory Aids
Mnemonic
Think: FERRIC (iron with a +3 charge) + CYANIC (related to cyanide, CN) + ACID. It's the acidic form of the 'ferricyanide' ion.
Watch out
Common Pitfalls
Translation Traps (for Russian speakers)
- Do not confuse with 'ферроцианистоводородная кислота' (ferrocyanic acid). The key distinction is 'ferri-' (+3) vs. 'ferro-' (+2).
- The '-ic' in 'ferricyanic' corresponds to the higher oxidation state of iron, analogous to other -ous/-ic pairs in chemistry.
Common Mistakes
- Misspelling as 'fericyanic' or 'ferrocyanic'.
- Incorrectly assuming it is a common laboratory acid like sulfuric or hydrochloric acid.
- Mispronouncing the 'cyanic' part as /saɪˈænɪk/ instead of /saɪˈænɪk/ is common but minor.
Practice
Quiz
What is the primary practical significance of ferricyanic acid?
FAQ
Frequently Asked Questions
As a strong acid derived from cyanide complexes, it would be highly corrosive and toxic, but it is not handled in pure form. Its salts require careful handling due to toxicity and oxidizing properties.
In advanced chemistry courses, historical chemistry texts, or technical papers discussing hexacyanoferrate(III) chemistry.
Ferricyanic acid contains iron in the +3 oxidation state (Fe³⁺), while ferrocyanic acid contains iron in the +2 state (Fe²⁺). Their salts have different colours and redox properties.
No. It is not commercially available as a pure substance. Instead, you purchase its salts, such as potassium ferricyanide, which are stable crystalline solids.