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.

關(guān)鍵詞:溫度洗滌劑洗滌次數(shù)

Key words: washing times of temperature detergent

氯化鉀產(chǎn)品有三個(gè)類別:I類為特種工業(yè)用氯化鉀，適用于電解法制取氫氧化鉀、氯酸鉀等。Π類為工業(yè)用氯化鉀，適用于化工行業(yè)中的各種鉀鹽的生產(chǎn)。Ⅲ類為農(nóng)業(yè)用氯化鉀，適用于配制復(fù)混肥或直接作為肥料施用。

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.

本文所論述的氯化鉀是適用于配制復(fù)混肥或直接作為肥料施用的產(chǎn)品。它是以白色或微紅色的結(jié)晶體存在的，主含量用氧化鉀來(lái)表示。氯化鉀產(chǎn)品的氧化鉀含量檢測(cè)時(shí)，應(yīng)注意以下幾個(gè)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:

溶液制備的溫度控制是首要條件

Temperature control of solution preparation is the first condition

按GB/T6678-2003《化工產(chǎn)品采樣總則》中6.6規(guī)定，檢測(cè)中要確定樣品的采樣單元數(shù)。采樣器由袋口的一角斜袋深的3/4處采樣，將采出的樣品混勻，用四分法縮分所要檢驗(yàn)的樣品量。因氯化鉀肥料吸水性強(qiáng)，故在制備樣品時(shí)動(dòng)作應(yīng)迅速。樣品制備后，稱取5g試樣，精確0.001g，加入150ml水，然后在不斷攪拌下加熱，微沸5min，取下冷卻20℃，移入500ml容量瓶，定容過(guò)濾后再吸取25.0ml于250.0ml的容量瓶中。這是一個(gè)很關(guān)鍵的環(huán)節(jié)。有一些檢驗(yàn)員為了一時(shí)方便，不是在水溫達(dá)到20℃時(shí)定容，而按常溫的水溫定容，結(jié)果是水溫高于20℃時(shí)，結(jié)果偏高；水溫低于20℃時(shí)，結(jié)果偏低。兩次定容造成兩次誤差，所以，準(zhǔn)確的檢驗(yàn)溫度是檢測(cè)結(jié)果準(zhǔn)確與否的關(guān)鍵。水溫高于20℃的檢測(cè)結(jié)果與20℃時(shí)的檢測(cè)結(jié)果比較見(jiàn)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 ℃.

洗滌劑、蒸餾水對(duì)檢測(cè)結(jié)果的影響

Influence of detergent and distilled water on test results

氧化鉀含量的測(cè)定等效采用ISO2051∶1976《工業(yè)用氯化鉀-鉀含量的測(cè)定——四苯硼鉀重量法》。在弱堿性介質(zhì)中，四苯硼鈉[NaB(C6H5)4]堿性溶液和洗滌液對(duì)檢測(cè)結(jié)果有直接影響。因?yàn)榕渲坪玫乃谋脚疴c很不穩(wěn)定，容易產(chǎn)生渾濁。如果使用前發(fā)現(xiàn)有混濁，要用中速濾紙過(guò)濾后再使用，否則檢測(cè)結(jié)果偏高。用洗滌液洗滌和用蒸餾水洗滌檢測(cè)，結(jié)果也不一樣。有些檢驗(yàn)員認(rèn)為配制洗滌液麻煩，用蒸餾水代替洗滌液，檢測(cè)結(jié)果就會(huì)偏低。蒸餾水的原始結(jié)果與洗滌劑的正確結(jié)果相關(guān)數(shù)據(jù)比較見(jiàn)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.

洗滌步驟是關(guān)鍵

Washing step is the key

檢測(cè)中，試液過(guò)濾后的洗滌步驟存在洗滌終點(diǎn)不夠明確的問(wèn)題。依據(jù)GB6549-1996《氯化鉀》規(guī)定，先抽濾上清液，再用洗滌液（即室溫下飽和的四苯硼鉀溶液）轉(zhuǎn)移沉淀過(guò)濾器中，繼續(xù)用以上洗滌液洗滌沉淀12次左右，每次洗滌液用量約為5ml。如果檢驗(yàn)員做不夠洗滌次數(shù)，在干燥后的坩堝上就能清晰見(jiàn)到粉紅色的物質(zhì)，這是未洗滌盡的氫氧化鈉與酚酞產(chǎn)生的物質(zhì)顏色，終將導(dǎo)致鉀含量偏高。因此，洗滌次數(shù)均不應(yīng)低于12次。洗滌次數(shù)少于12次的原始結(jié)果與不少于12次的正確結(jié)果比較見(jiàn)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.

結(jié)論

conclusion

綜上所述，在氯化鉀產(chǎn)品的主含量氧化鉀檢測(cè)中，對(duì)幾個(gè)關(guān)鍵環(huán)節(jié)必須給予足夠的重視，對(duì)可能產(chǎn)生誤差的各種因素要加以避免和克服，才能保證檢測(cè)結(jié)果的準(zhǔn)確度。

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.

溫度洗滌劑與蒸餾水洗滌次數(shù)

Washing times of temperature detergent and distilled water

原始結(jié)果正確結(jié)果原始結(jié)果正確結(jié)果原始結(jié)果正確結(jié)果

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

（大于20℃時(shí)）（20℃時(shí)）

(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