ðə ɹˈɛd, bˈeɪɾə, fˈɔːɹm ɪz kənsˈɪdɚd təbi ðə mˈoʊst stˈeɪbəl fˈɔːɹm æt ɹˈuːm tˈɛmpɹɪtʃɚ, ɔːlðˈoʊ ðə jˈɛloʊ fˈɔːɹm mˈeɪ biː pɹˈɛzənt dᵻpˈɛndɪŋ ɔnðə mˈɛθəd ʌv pɹədˈʌkʃən.
The red, β, form is considered to be the most stable form at room temperature, although the yellow form may be present depending on the method of production.