in proportion of 1 to 7 下面是例句：
方法：
用壳聚糖和羧甲基壳聚按3：1的比例采用冷冻干燥法制成壳聚糖复合导管；
Methods: Complex chitosan conduits were made from chitosan and carboxymethylchitosan by freeze drying method in
proportion of 3 to
1.
也可以直接用 by 1:7
英语翻译.按1：7的比例加入试剂,介词用in 还是用with 或者是at?