1、GB1078.8-894.2测定4.2.1折光计在测定前按说明书进行校正。4.2.2分开折光计的两面棱镜，以脱脂棉蘸乙醚或酒精擦净。4.2.3用末端熔圆之玻璃棒蘸取均匀试样汁液(4.1)23滴，仔细滴于折光计棱镜平面之中央（注意勿使玻璃棒触及棱镜)。4.2.4迅速闭合上下二棱镜，静置1mn,要求液体均匀无气泡并充满视野。4.2.5对准光源，由目镜观察，调节指示规，使视野分成明暗两部，再旋动微调螺旋，使两部界限明晰，其分线恰在接物镜的十字交叉点上。4.2.6如折光计读数标尺刻度为百分数，即可溶性固形物的百分率，按可溶性固形物对温度校正表(表1)换算成20时标准的可溶性固形物百分率。表1可溶性固形
2、物对温度校正表可溶性固形物含量读数，%度()106202530o506070减校正值150.290.310.330.340.340.350.370.380.390.40160.240.250.260.270.280.280.300.300.310.32170.180.190.200.210.210.210.220.230.230.24180.130.130.140.140.140.140.150.150.160.16190.060.060.070.070.070.070.080.080.080.08加华正值210.070.070.070.070.080.080.080.080.080.08220.130.140.140.150.150.150.150.160.160.16230.200.210.220.220.230.230.230.240.240.24240.270.280.290.300.300.310.310.310.320.32250.350.360.370.380.380.390.400.400.400.404,2.7如折光计读数标尺刻度为折光率，可读出其折光率，然后按折光率与可溶性固形物换算表（表2）查得样品中之可溶性固形物的百分率，再按可溶性固形物对温度校正表（表1）换算成20标准的可溶性固形物百分率。2
