The word "ceridin" is spelled with a hard "c" and a long "i" sound. In IPA phonetic transcription, it would be represented as /sɛrɪdɪn/. The first syllable, "cer", is pronounced with an "s" sound rather than "c" because it is followed by the vowel "e". The "i" in the second and third syllables is pronounced as a long "i" sound, like the "i" in "nine". Overall, the phonetic spelling of "ceridin" accurately reflects the pronunciation of the word.
Cerolin, the proprietary name for a preparation said to be the active principle of yeast; employed in acne, furunculosis, and chronic constipation in doses of 5 to 8 grains (0.3-0.5).
A practical medical dictionary. By Stedman, Thomas Lathrop. Published 1920.