wall saltpetre

例句：

1. 1.The wall saltpetre was used to make the bricks stronger.
   用盐石制作砖块使其更坚固。
2. 2.The saltpetre in the soil is essential for plant growth.
   土壤中的盐石对植物生长至关重要。
3. 3.The wall saltpetre was used as a preservative for food products.
   盐石被用作食品产品的防腐剂。