▁minor ▁medical ▁applications , ▁the ▁first ▁commercial ▁use ▁was ▁the ▁dag uer re ot ype . ▁In ▁ 1 8 4 0 , ▁b rom ine ▁was ▁discovered ▁to ▁have ▁some ▁advantages ▁over ▁the ▁previously ▁used ▁i od ine ▁v apor ▁to ▁create ▁the ▁light ▁sensitive ▁silver ▁hal ide ▁layer ▁in ▁dag uer re ot yp y . ▁ ▁Pot ass ium ▁b rom ide ▁and ▁sod ium ▁b rom ide ▁were ▁used ▁as ▁ant icon v uls ants ▁and ▁sed atives ▁in ▁the ▁late ▁ 1 9 th ▁and ▁early ▁ 2 0 th ▁centuries , ▁but ▁were ▁gradually ▁su pers eded ▁by ▁ch lor al ▁hyd rate ▁and ▁then ▁by ▁the ▁bar bit ur ates . ▁In ▁the ▁early ▁years ▁of ▁the ▁First ▁World ▁War , ▁b rom ine ▁comp ounds ▁such ▁as ▁x y ly l ▁b rom ide ▁were ▁used ▁as ▁poison ▁gas . ▁ ▁Properties ▁ ▁B rom ine ▁is ▁the ▁third ▁hal ogen , ▁being ▁a ▁non met al ▁in ▁group ▁ 1 7 ▁of ▁the ▁periodic ▁table . ▁Its ▁properties ▁are ▁thus ▁similar ▁to ▁those ▁of ▁flu or ine , ▁ch lor ine , ▁and ▁i od ine , ▁and ▁tend ▁to ▁be ▁intermediate ▁between ▁those ▁of ▁the ▁two ▁neighbour ing ▁hal og ens , ▁ch lor ine ▁and ▁i od ine . ▁B rom ine ▁has ▁the ▁electron ▁configuration ▁[ Ar ] 3 d 1 0 4 s 2 4 p 5 , ▁with ▁the ▁seven ▁electrons ▁in ▁the ▁fourth ▁and ▁outer most ▁shell ▁acting