甲酸具有还原性，从理论上也是不难理解的。但关于它还原氢氧化铜的实验，在教学中做起实验来没有把握，达不到预期的效果。为此从改进实验条件人手进行探索，以达到较好的效果。

Formic acid has reducibility, which is not difficult to understand theoretically. But in the experiment of reducing copper hydroxide with it, it is not sure to do the experiment in teaching, and it can not achieve the expected effect. Therefore, we should improve the experimental conditions to achieve better results.

1.试剂与配制

1. Reagent and preparation

5％CuSO4溶液：7.4g CuSO4·5H2O溶于93.6ml水中，

5% CuSO4 solution: 7.4g CuSO4 · 5H2O was dissolved in 93.6ml water,

10％NaOH溶液：11.1g NaOH配100ml溶液

10% NaOH solution: 11.1g NaOH mixed with 100ml solution

甲酸浓溶液：～80％(原装)

Formic acid concentrated solution: ～ 80% (original)
                            

2.操作与现象

2. Operation and phenomenon

为了便于观察和对比，令反应在U形管中进行(亦可甲试管)，采用水浴加热(90－95℃)。 先在U形管内倒入约20－30m110％NaOH溶液，使液面距管口约5cm，再从管口(I)小心滴入3－5滴5％CuSO4溶液，液面有Cu(OH)2沉淀析出，然后慢慢注入8－10滴甲酸浓溶液，沉淀溶解，液层呈蓝色(切勿振荡)。将U形管置水浴中加热(90－95℃)，约2分钟后，在蓝色液层和无色液层界面处出现薄层土红色沌液(含Cu2O)。随着反应的进行，土红色沌液层不断扩大，约5分钟后全部蓝色液层变为土红色浊液。

For the convenience of observation and comparison, the reaction was carried out in a U-tube (or a test tube) and heated in a water bath (90-95 ℃). First, pour about 20-30 ml 110% NaOH solution into the U-shaped tube to make the liquid level about 5 cm away from the tube orifice. Then, carefully drop 3-5 drops of 5% CuSO4 solution from the tube orifice (I). There is Cu (OH) 2 Precipitation on the liquid level. Then slowly inject 8-10 drops of concentrated formic acid solution. The precipitation dissolves and the liquid layer is blue (do not shake). After heating the U-shaped tube in a water bath (90-95 ℃) for about 2 minutes, a thin layer of earth red chaotic liquid (containing Cu2O) appeared at the interface between the blue liquid layer and the colorless liquid layer. As the reaction proceeds, the turquoise chaotic liquid layer expands, and after about 5 minutes, all the blue liquid layers turn into Turquoise turbid liquid.

再在管口(Ⅱ)滴入3－5滴5％CuSO4溶液，立即有黑色胶凝物(在热碱中生成的Cu(OH)2立即分解为CuO沉淀，然后滴入2-3滴甲酸溶液。不久，液面出现土红色浊液层，且部分黑色胶凝物浮于液面，渐变为土红色。

Then 3-5 drops of 5% CuSO4 solution were dropped into the nozzle (II), and immediately the Black Gel (Cu (OH) 2 formed in hot alkali) was decomposed into CuO precipitate, and then 2-3 drops of formic acid solution were dropped. Soon, a soil red turbid layer appeared on the liquid surface, and some black gels floated on the liquid surface and gradually turned into soil red.

含有Cu2O的浊液层所以呈土红色，一是还原产物(Cu2O)的量较少，二是混有CuO2，但都不影响实验的良好效果。

The results show that the turbidity layer containing Cu2O is earthy red, one is that the amount of reduction product (Cu2O) is less, the other is that it is mixed with CuO2, but it does not affect the good effect of the experiment.