十字交叉法，用于求混和物中各组成物质的质量比或物质的量之比、确能事半功倍，但理解不同，用法各异，其效果也迎然不同。因此，如何在透彻理解的前提下，正确利用题目条件，巧用十字交叉法求解，常备受关注。下面列举三例，以供参考。例1：硫酸钠与亚硫酸钠混和物中含硫25％ Cross method, used to find the mixture of substances in the mass ratio or the ratio of the amount of substance, can do more with less, but to understand different, different usage, the effect is obviously different. Therefore, under the premise of thorough understanding, the correct use of the subject conditions, clever use of cross method to solve, often of concern. Here are three examples for reference. Example 1: Sulfuric acid and sodium sulfite mixture sulfur 25%