▁H ague ▁– ▁offered ▁him ▁a ▁trip ▁to ▁Le iden ▁and ▁co operation ▁with ▁the ▁Institute ▁of ▁Low ▁Tem per atures ▁in ▁Le iden , ▁where ▁professor ▁H . ▁K . ▁K amer ling h - On nes ▁and ▁( l ater ) ▁Wille m ▁Ke es om ▁studied ▁the ▁die lect ric ▁constant ▁of ▁liquid ▁hel ium ▁at ▁various ▁temper atures . ▁The ▁theoretical ▁experiments ▁led ▁him ▁to ▁the ▁discovery ▁of ▁two ▁liquid ▁phases ▁of ▁hel ium ▁and ▁solid ification ▁of ▁hel ium ▁what ▁Mie cz ys ław ▁Wolf ke ▁considered ▁as ▁the ▁third ▁of ▁his ▁greatest ▁achiev ements . ▁In ▁the ▁early ▁th irt ies ▁Wolf ke ▁started ▁to ▁organ ize ▁the ▁separated ▁Institute ▁of ▁Low ▁Tem per atures ▁at ▁Wars aw ▁University ▁of ▁Technology , ▁even ▁running ▁the ▁first ▁installation . ▁ ▁In ▁ 1 9 2 7 ▁Wolf ke ▁worked ▁on ▁the ▁liquid ▁hel ium ▁die lect ric ▁constant ▁and ▁in ▁the ▁next ▁year ▁on ▁the ▁association ▁in ▁liquid ▁die lect rics . ▁He ▁also ▁started ▁co operation ▁with ▁the ▁Polish ▁Army ▁in ▁Tem por ary ▁Ad vis ory ▁and ▁Scient ific ▁Committee ▁and ▁did ▁lots ▁of ▁invent ions ▁for ▁the ▁soldiers . ▁ ▁In ▁ 1 9 3 0 ▁he ▁presented ▁the ▁theory ▁of ▁multiple ▁associations . ▁He ▁also ▁conducted ▁the ▁research ▁on ▁the ▁point ▁of ▁change ▁in ▁the ▁liquid ▁phase ▁and ▁worked ▁on ▁the ▁experimental ▁finding ▁of ▁light ▁mole cules . ▁Ein stein ▁mentioned ▁his ▁work ▁at ▁the ▁Berlin ▁Academy ▁of ▁Science . ▁ ▁In ▁ 1