▁the ▁excited ▁mole cules ▁formed ▁in ▁the ▁fl ame . ▁Usually ▁o xygen ▁is ▁involved , ▁but ▁hydro gen ▁burning ▁in ▁ch lor ine ▁also ▁produces ▁a ▁fl ame , ▁producing ▁hydro gen ▁ch lor ide ▁( H Cl ). ▁Other ▁possible ▁combinations ▁producing ▁fl ames , ▁amongst ▁many , ▁are ▁flu or ine ▁and ▁hydro gen , ▁and ▁hyd raz ine ▁and ▁nit ro gen ▁t etro x ide . ▁H ydro gen ▁and ▁hyd raz ine / UD M H ▁fl ames ▁are ▁similarly ▁pale ▁blue , ▁while ▁burning ▁bor on ▁and ▁its ▁comp ounds , ▁evaluated ▁in ▁mid - 2 0 th ▁century ▁as ▁a ▁high ▁energy ▁fuel ▁for ▁jet ▁and ▁ro cket ▁engines , ▁em its ▁inten se ▁green ▁fl ame , ▁leading ▁to ▁its ▁inform al ▁nick name ▁of ▁" Green ▁Dragon ". ▁ ▁The ▁g low ▁of ▁a ▁fl ame ▁is ▁complex . ▁Black - body ▁radiation ▁is ▁em itted ▁from ▁so ot , ▁gas , ▁and ▁fuel ▁particles , ▁though ▁the ▁so ot ▁particles ▁are ▁too ▁small ▁to ▁behave ▁like ▁perfect ▁black b od ies . ▁There ▁is ▁also ▁phot on ▁emission ▁by ▁de - ex c ited ▁atoms ▁and ▁mole cules ▁in ▁the ▁g ases . ▁Much ▁of ▁the ▁radiation ▁is ▁em itted ▁in ▁the ▁visible ▁and ▁inf ra red ▁bands . ▁The ▁color ▁depends ▁on ▁temperature ▁for ▁the ▁black - body ▁radiation , ▁and ▁on ▁chemical ▁make up ▁for ▁the ▁emission ▁spect ra . ▁The ▁dominant ▁color ▁in ▁a ▁fl ame ▁changes ▁with ▁temperature