Abstract: several problems should be paid attention to when detecting the main content of potassium oxide in potassium chloride products. In this paper, the influences of sample preparation, reagent stability, temperature, detergent and distilled water, washing times after filtration, etc. on the test results are described.

关键词:温度洗涤剂洗涤次数

Key words: washing times of temperature detergent

氯化钾产品有三个类别:I类为特种工业用氯化钾，适用于电解法制取氢氧化钾、氯酸钾等。Π类为工业用氯化钾，适用于化工行业中的各种钾盐的生产。Ⅲ类为农业用氯化钾，适用于配制复混肥或直接作为肥料施用。

There are three categories of potassium chloride products: Category I is special industrial potassium chloride, which is suitable for electrolytic preparation of potassium hydroxide, potassium chlorate, etc. Π is industrial potassium chloride, which is suitable for the production of various potassium salts in the chemical industry. Class III is potassium chloride for agricultural use, which is suitable for the preparation of compound fertilizer or direct application as fertilizer.

本文所论述的氯化钾是适用于配制复混肥或直接作为肥料施用的产品。它是以白色或微红色的结晶体存在的，主含量用氧化钾来表示。氯化钾产品的氧化钾含量检测时，应注意以下几个方面：

The potassium chloride discussed in this paper is a product suitable for compounding compound fertilizer or applying directly as fertilizer. It is a white or reddish crystal, the main content of potassium oxide to express. In the detection of potassium oxide content of potassium chloride products, the following aspects should be paid attention to:

溶液制备的温度控制是首要条件

Temperature control of solution preparation is the first condition

按GB/T6678-2003《化工产品采样总则》中6.6规定，检测中要确定样品的采样单元数。采样器由袋口的一角斜袋深的3/4处采样，将采出的样品混匀，用四分法缩分所要检验的样品量。因氯化钾肥料吸水性强，故在制备样品时动作应迅速。样品制备后，称取5g试样，精确0.001g，加入150ml水，然后在不断搅拌下加热，微沸5min，取下冷却20℃，移入500ml容量瓶，定容过滤后再吸取25.0ml于250.0ml的容量瓶中。这是一个很关键的环节。有一些检验员为了一时方便，不是在水温达到20℃时定容，而按常温的水温定容，结果是水温高于20℃时，结果偏高；水温低于20℃时，结果偏低。两次定容造成两次误差，所以，准确的检验温度是检测结果准确与否的关键。水温高于20℃的检测结果与20℃时的检测结果比较见表1。

According to 6.6 of general rules for sampling of chemical products (GB / t6678-2003), the number of sampling units shall be determined during the test. The sampler is inclined from one corner of the bag mouth to 3 / 4 of the bag depth to sample, mix the samples, and reduce them to the sample quantity to be inspected by quartering method. Because potassium chloride fertilizer has strong water absorption, it should act quickly when preparing samples. After sample preparation, weigh 5g of sample, accurate to 0.001g, add 150ml of water, heat it under constant agitation, boil it for 5min, take it down and cool it to 20 ℃, transfer it to 500ml volumetric flask, filter it at constant volume, then suck 25.0ml into 250.0ml volumetric flask. This is a very critical link. For the convenience of some inspectors, instead of constant volume when the water temperature reaches 20 ℃, the constant volume is based on the normal temperature water temperature. As a result, when the water temperature is higher than 20 ℃, the result is higher; when the water temperature is lower than 20 ℃, the result is lower. Two times of constant volume results in two times of error, so the key to the accuracy of test results is to check the temperature accurately. See Table 1 for the comparison between the test results when the water temperature is higher than 20 ℃ and the test results when the water temperature is 20 ℃.

洗涤剂、蒸馏水对检测结果的影响

Influence of detergent and distilled water on test results

氧化钾含量的测定等效采用ISO2051∶1976《工业用氯化钾-钾含量的测定——四苯硼钾重量法》。在弱碱性介质中，四苯硼钠[NaB(C6H5)4]碱性溶液和洗涤液对检测结果有直接影响。因为配制好的四苯硼钠很不稳定，容易产生浑浊。如果使用前发现有混浊，要用中速滤纸过滤后再使用，否则检测结果偏高。用洗涤液洗涤和用蒸馏水洗涤检测，结果也不一样。有些检验员认为配制洗涤液麻烦，用蒸馏水代替洗涤液，检测结果就会偏低。蒸馏水的原始结果与洗涤剂的正确结果相关数据比较见表1。

The determination of potassium oxide content is equivalent to iso2051:1976 determination of potassium chloride potassium content for industrial use - potassium tetraphenylboron gravimetric method. In the weak alkaline medium, sodium tetraphenylborate [nab (C6H5) 4] alkaline solution and washing solution have a direct impact on the test results. Because the prepared sodium tetraphenylboron is very unstable, it is easy to produce turbidity. If turbidity is found before use, filter with medium speed filter paper before use, otherwise the test result is too high. Washing with washing liquid and testing with distilled water, the results are not the same. Some inspectors think that it is troublesome to prepare washing solution. If distilled water is used instead of washing solution, the test result will be lower. See Table 1 for the comparison between the original results of distilled water and the correct results of detergent.

洗涤步骤是关键

Washing step is the key

检测中，试液过滤后的洗涤步骤存在洗涤终点不够明确的问题。依据GB6549-1996《氯化钾》规定，先抽滤上清液，再用洗涤液（即室温下饱和的四苯硼钾溶液）转移沉淀过滤器中，继续用以上洗涤液洗涤沉淀12次左右，每次洗涤液用量约为5ml。如果检验员做不够洗涤次数，在干燥后的坩埚上就能清晰见到粉红色的物质，这是未洗涤尽的氢氧化钠与酚酞产生的物质颜色，终将导致钾含量偏高。因此，洗涤次数均不应低于12次。洗涤次数少于12次的原始结果与不少于12次的正确结果比较见表1。

In the test, there is a problem that the end-point of washing is not clear after the test solution is filtered. According to the provisions of potassium chloride (gb6549-1996), the supernatant shall be pumped and filtered first, and then the detergent (i.e. saturated potassium tetraphenylborate solution at room temperature) shall be transferred to the filter for sedimentation. The above detergent shall be used for washing and sedimentation for about 12 times, and the dosage of each detergent is about 5ml. If the inspector does not wash for enough times, the pink material can be clearly seen on the dried crucible, which is the color of the material produced by the unwashed sodium hydroxide and phenolphthalein, which will eventually lead to high potassium content. Therefore, the washing times should not be less than 12 times. See Table 1 for the comparison between the original results with less than 12 washing times and the correct results with more than 12 washing times.

结论

conclusion

综上所述，在氯化钾产品的主含量氧化钾检测中，对几个关键环节必须给予足够的重视，对可能产生误差的各种因素要加以避免和克服，才能保证检测结果的准确度。

In conclusion, in the detection of potassium oxide in the main content of potassium chloride products, enough attention must be paid to several key links, and various factors that may cause errors must be avoided and overcome to ensure the accuracy of the detection results.

温度洗涤剂与蒸馏水洗涤次数

Washing times of temperature detergent and distilled water

原始结果正确结果原始结果正确结果原始结果正确结果

Original result correct result original result correct result original result correct result

（大于20℃时）（20℃时）

(above 20 ℃) (at 20 ℃)

58.1757.7557.5257.7560.457.75

58.1757.7557.5257.7560.457.75

58.2157.8257.5657.8260.857.82

58.2157.8257.5657.8260.857.82