毛細管上升法

測定原理(li)：

將一支毛(mao)(mao)細(xi)(xi)管(guan)插(cha)入液(ye)(ye)體(ti)(ti)(ti)(ti)中,液(ye)(ye)體(ti)(ti)(ti)(ti)將沿(yan)毛(mao)(mao)細(xi)(xi)管(guan)上(shang)(shang)升(sheng)(sheng),升(sheng)(sheng)到(dao)(dao)一定(ding)高度后,毛(mao)(mao)細(xi)(xi)管(guan)內外液(ye)(ye)體(ti)(ti)(ti)(ti)將達到(dao)(dao)平衡(heng)狀態,液(ye)(ye)體(ti)(ti)(ti)(ti)就不再(zai)上(shang)(shang)升(sheng)(sheng)了。此(ci)時,液(ye)(ye)面(mian)對液(ye)(ye)體(ti)(ti)(ti)(ti)所施加的(de)向(xiang)(xiang)上(shang)(shang)的(de)拉(la)力與液(ye)(ye)體(ti)(ti)(ti)(ti)向(xiang)(xiang)下(xia)的(de)力相等。則表(biao)面(mian)張力：γ=ρghr*r/(2cosθ)

式中(zhong)γ為(wei)表面張力,r為(wei)毛細管(guan)的(de)半徑,h為(wei)毛細管(guan)中(zhong)液(ye)面上(shang)升(sheng)的(de)高(gao)度,ρ為(wei)測(ce)量液(ye)體的(de)密度,g為(wei)當地的(de)重力加速度,θ為(wei)液(ye)體與(yu)管(guan)壁的(de)接觸角。

Wilhelmy盤法

用(yong)鉑(bo)片(pian)(pian)、云母片(pian)(pian)或顯微鏡蓋玻(bo)片(pian)(pian)掛在扭(niu)力(li)天平或鏈式(shi)天平上(shang),測定當(dang)片(pian)(pian)的底(di)邊平行面(mian)剛好接觸液(ye)面(mian)時的壓力(li),由此(ci)得表面(mian)張(zhang)力(li),公式(shi)為:

式中,W總為(wei)(wei)薄(bo)片(pian)與液(ye)面拉脫時的最大拉力,W片(pian)為(wei)(wei)薄(bo)片(pian)的重力,l為(wei)(wei)薄(bo)片(pian)的寬度,薄(bo)片(pian)與液(ye)體的接觸的周長(chang)近似為(wei)(wei)2l,φ為(wei)(wei)薄(bo)片(pian)與液(ye)體的接觸角。