Melamine is pure white monoclinic crystal, tasteless, and its density is 1.573g/cm3 (16℃). Normal pressure melting point 354℃ (decomposition); Rapid heating sublimation, sublimation temperature is 300℃. Soluble in hot water, slightly soluble in cold water, slightly soluble in hot ethanol, insoluble in ether, benzene and carbon tetrachloride, soluble in methanol, formaldehyde, acetic acid, hot ethylene glycol, glycerol, pyridine, etc. Low toxicity. It is generally stable, but it may release cyanide at high temperature.
It is weakly alkaline (pKb=8) and can form melamine salt with hydrochloric acid, sulfuric acid, nitric acid, acetic acid and oxalic acid. Under neutral or weak alkaline conditions, all kinds of hydroxymethyl melamine are condensed with formaldehyde, but under weak acidic conditions (pH 5.5 ~ 6.5), they are condensed with hydroxymethyl derivatives to produce resin products. When hydrolyzed with strong acid or strong alkali aqueous solution, amino groups are gradually replaced by hydroxyl groups and become cyanuric acid diamide, which is further hydrolyzed to form cyanuric acid monoamide, and finally cyanuric acid is generated.
At present, melamine is considered to be slightly toxic, and the lethal dose to rats is above 3 g/kg body weight. According to an experimental report of 1945, rats, rabbits and dogs were fed with large doses of melamine, and no obvious poisoning phenomenon was found. Long-term intake of melamine in animals will cause damage to reproductive and urinary systems, bladder and kidney calculi, and further induce bladder cancer. 1994 Volume III of the International Handbook of Chemical Safety and the International Chemical Safety Card jointly edited by the International Chemical Safety Agency and the European Commission only show that long-term or repeated intake of melamine may affect the kidneys and bladder, leading to stones. However, the preliminary investigation of pet food pollution in the United States in 2007 showed that wheat protein powder mixed with melamine ≤6.6% was the cause of pet food poisoning, which put a question mark on the above conclusion of slight toxicity. However, for safety reasons, melamine tableware will be marked "Do not use in the microwave oven".
On September 12, 2008, China's Ministry of Health issued the "Diagnosis and Treatment Plan for Urinary Calculi in Infants Related to Eating Contaminated Sanlu Infant Formula Milk Powder", which can be used as a reference for relevant parties.
It is pointed out in the plan that most stones involve bilateral collecting system and bilateral ureters, which is different from the clinical manifestations of adult urinary calculi, and the probability of multiple stones affecting renal function is high. Because most children do not have the ability to complain about symptoms, parents need to strengthen the observation of related children, and relying on abdominal B-ultrasound and/or CT examination is helpful for early diagnosis. In terms of treatment, there is no specific antidote for the toxic effect of melamine at present, and clinical treatment mainly depends on symptomatic support. If necessary, surgical intervention can be considered to reduce the risk of long-term damage to children's renal function. Early diagnosis and treatment is the key to a child's early recovery.
Melamine is a low toxic chemical raw material. The results of animal experiments show that it is metabolized quickly in animals and will not remain, which mainly affects the urinary system.
There is an obvious dose-effect relationship between the dose of melamine and clinical diseases. The maximum tolerance of infants to melamine is per kilogram of milk powder 15 mg. Experts' risk assessment of contaminated infant formula shows that, taking an infant weighing 7 kg as an example, assuming daily intake of 150 g of milk powder, its safety preset value is 15 mg/kg of milk powder.
According to the standards of the US Food and Drug Administration, the daily tolerable intake of melamine is 0.63 mg/kg body weight per day.
List of batches of melamine detected in liquid milk
Company serial number Product name specification model trademark production date/batch of melamine (mg/kg)
Mengniu 1 Mengniu (Wuhan) Friends of Friends Dairy Co., Ltd. Walnut milk 200ml/ Bag Friends of Friends 200809 10 0.765
Mengniu 2 Inner Mongolia Mengniu Dairy (Group) Co., Ltd. Mengniu high-calcium low-fat milk 250ml/ case Mengniu 2008.08.07.0.8
Mengniu 3 Inner Mongolia Mengniu Dairy (Group) Co., Ltd. Full-fat sterilized pure milk 250ml/ case Mengniu 2008.09.0 1. 1.0
Mengniu 4 Inner Mongolia Mengniu Dairy (Group) Co., Ltd. High calcium and low fat milk 250ml/ case Mengniu 2008.08.0 1. 1.5
Mengniu 5 Inner Mongolia Mengniu Dairy (Group) Co., Ltd. Breakfast Milk (Maixiang Type) 250ml/ bag Mengniu 200808 14 1.9
Mengniu 6 Inner Mongolia Mengniu Dairy (Group) Co., Ltd. Mengniu breakfast milk 250ml/ box Mengniu 2008.07.26/x 2.57
Mengniu 7 Inner Mongolia Mengniu Dairy (Group) Co., Ltd. Miaodian 250ml/ carton Mengniu 20080728/W2063 438+07
Mengniu 8 Mengniu Dairy (Beijing) Co., Ltd. Xylitol Yogurt 2kg/ bottle Mengniu 20080806 3.52
Mengniu 9 Inner Mongolia Mengniu Dairy (Group) Co., Ltd. High calcium and low fat milk 243ml(250g)/ Bag Mengniu 20080908/C206/GAfb 4.2
Mengniu 10 Mengniu dairy (Maanshan) co., ltd. Mengniu daguo yogurt 160g/ case Mengniu M200809036.8 (sample a)
Mengniu 1 1 Mengniu Dairy (Maanshan) Co., Ltd. Mengniu Daguo Yogurt 160g/ case Mengniu M200809037 (sample B)
Yili 1 Jinan Yili Dairy Co., Ltd. Yili Mango+Yellow Peach Yogurt 125g/ carton Yili 2008.09.07.0.69
Yili 2 Inner Mongolia Yili Industrial Group Co., Ltd. Yogurt (papaya+sweet orange) 125g/ bottle Yili 20080903 1.02
3 Yili Inner Mongolia Yili Industrial Group Co., Ltd. Pure milk 220ml/ bag Yili 2008.09. 13.2
Yili 4 Inner Mongolia Yili Industrial Group Co., Ltd. skim milk 250ml/ box Yili 20080820 2.9
Yili 5 Inner Mongolia Yili Industrial Group Co., Ltd. Pure milk 220ml/ bag Yili 20080905MIAC6 5.5
Yili 6 Inner Mongolia Yili Industrial Group Co., Ltd. Pure milk 242ml/ bag Yili 20080906/LIA09 8
Yili 7 Inner Mongolia Yili Industrial Group Co., Ltd. High calcium and low fat milk 250ml/ box Yili 200808 19 8.4
Guangming 1 Beijing Guangming Jianneng Dairy Co., Ltd. Guangming Yogurt (original flavor) 180g/ BagGuangming 2008.09. 12 0.6
Guangming 2 Wuhan Guangming Dairy Co., Ltd. Original Yogurt 180g/ Box Guangming 2008-09- 13.45438+0
Guangming 3 Beijing Guangming Jianneng Dairy Co., Ltd. Original Yogurt 100g/ Cup Guangming 200809 10A 3.5
Guangming 4 Beijing Guangming Jianneng Dairy Co., Ltd. Big Fruit Strawberry Yogurt 450g/ box Guangming 20080902BC 4.8
Guangming 5 Bright Dairy Co., Ltd. Probiotic Excellent Cheese (original flavor) 190g/ jar Guangming B20080908C 5.65
Guangming 6 Beijing Guangming Jianneng Dairy Co., Ltd. Yogurt Yogurt (original flavor) 580 g/bottle Guangming B20080909A 8.6