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67-72-1

67-72-1结构式
67-72-1结构式
  • 常用中文名:六氯乙烷
  • 常用英文名:Hexachloroethane
  • CAS号:67-72-1
  • 分子式:C2Cl6
  • 分子量:236.739
  • 相关类别: 有机原料 烃类化合物及其衍生物 烃类卤化物
  • 发布时间:2018-09-04 00:08:09
  • 更新时间:2024-01-02 12:44:39

  • 【用途一】
    用作润滑油添加剂,亦可用于制造杀虫剂、驱虫剂、烟幕等
    【用途二】
    该品用作溶剂和用于生产氟里昂-113、农药、医药、兽药、发烟剂、除泡剂、铝制品的脱气剂、脱氧剂(铝、镁、铜及其合金)、切消油添加剂以及聚氯乙烯助增塑剂、有机合成中间体。六氯乙烷与锌粉、氯化铵、过氯酸铵等按比例混合可用作烟雾生成剂,六氯乙烷还用作樟脑代用品和橡胶硫化促进剂等。六氯乙烷本身也是一种兽用驱虫药。主要用于反刍兽肝蛭病及胃蛭病,其他睾吸虫病和线虫病等。
    【用途三】
    溶剂,防腐剂。该品用作溶剂和用于生产氟里昂-113、农药、医药、兽药、发烟剂、除泡剂、铝制品的脱气剂、脱氧剂(铝、镁、铜及其合金)、切消油添加剂以及聚氯乙烯助增塑剂、有机合成中间体。六氯乙烷与锌粉、氯化铵、过氯酸铵等按比例混合可用作烟雾生成剂,六氯乙烷还用作樟脑代用品和橡胶硫化促进剂等。六氯乙烷本身也是一种兽用驱虫药。主要用于反刍兽肝蛭病及胃蛭病,其他睾吸虫病和线虫病等。

化源商城直购

中文名 六氯乙烷
英文名 hexachloroethane
中文别名 全氯乙烷
六氯化二碳
六氯化碳
英文别名 MFCD00000799
Hexachloroethane
EINECS 200-666-4
Ethane, 1,1,1,2,2,2-hexachloro-
密度 1.8±0.1 g/cm3
沸点 186.8±0.0 °C at 760 mmHg
熔点 184 °C
分子式 C2Cl6
分子量 236.739
闪点 61.3±15.8 °C
精确质量 233.813110
LogP 4.47
外观性状 白色结晶粉末
蒸汽密度 8.16 (vs air)
蒸汽压 0.9±0.3 mmHg at 25°C
折射率 1.533
储存条件

储存注意事项储存于阴凉、通风的库房。远离火种、热源。包装密封。应与氧化剂、碱类、食用化学品分开存放,切忌混储。储区应备有合适的材料收容泄漏物。

稳定性

1.六氯乙烷能升华,在空气中逐渐挥发。化学性质稳定,常温下与水接触不发生分解。在酸或碱的水溶液中也不反应。与氯化锌反应生成四氯化碳。用锌和硫酸还原则生成四氯乙烯。高温热解生成四氯化碳、四氯乙烯和氯气。

2.稳定性 稳定

3.禁配物 强氧化剂、强碱、金属等

4.避免接触的条件 光照、受热

5.聚合危害 不聚合

6.分解产物 氯化氢、光气

水溶解性 0.05 g/L (22 ºC)
分子结构

1、摩尔折射率:40.34

2、摩尔体积(cm3/mol):129.9

3、等张比容(90.2K):332.5

4、表面张力(dyne/cm):42.8

5、极化率(10-24cm3):15.99

计算化学

1.疏水参数计算参考值(XlogP):无

2.氢键供体数量:0

3.氢键受体数量:0

4.可旋转化学键数量:0

5.互变异构体数量:无

6.拓扑分子极性表面积0

7.重原子数量:8

8.表面电荷:0

9.复杂度:61.5

10.同位素原子数量:0

11.确定原子立构中心数量:0

12.不确定原子立构中心数量:0

13.确定化学键立构中心数量:0

14.不确定化学键立构中心数量:0

15.共价键单元数量:1

更多

1.性状:无色结晶,有樟脑样气味。

2.熔点(升华,℃):186

3.沸点(℃):186(103.34kPa,升华)

4.相对密度(水=1):2.09

5.相对蒸气密度(空气=1):8.16

6.饱和蒸气压(kPa):0.13(32.7℃)

7.临界压力(MPa):3.34

8.辛醇/水分配系数:3.82~4.19

9.溶解性:不溶于水,溶于乙醇、乙醚、苯、氯仿、油类等多数有机溶剂。

10.气相标准声称热(焓)( kJ·mol-1) :-138.9

11.气相标准熵(J·mol-1·K-1) :398.85

12.气相标准生成自由能( kJ·mol-1):-54.9

13.气相标准热熔(J·mol-1·K-1):136.73

14.液相标准声称热(焓)( kJ·mol-1):-187.6

15.液相标准熵(J·mol-1·K-1) :245.6

16.液相标准生成自由能( kJ·mol-1):-83.47

17.液相标准热熔(J·mol-1·K-1):196.2

18.蒸发热(KJ/kg,b.p.):194.2

19.燃烧热(KJ/mol,20ºC,固体):461

20.生成热(KJ/mol,20ºC,结晶):226

21.生成热(KJ/mol,20ºC,气体):154.9

22.比热容(KJ/(kg·K),25ºC,定压):0.729

国标编号: 61558
CAS: 67-72-1
中文名称: 六氯乙烷
英文名称: hexachloroethane;carbon hexachloride
别 名: 六氯化碳
分子式: C2Cl6;CCl3CCl3
分子量: 236.76
熔 点: 186℃/升华 沸点:186
密 度: 相对密度(水=1)2.09
蒸汽压: 32.7℃
溶解性: 不溶于水,溶于醇、苯、氯仿、油类等多数有机溶剂
稳定性: 稳定
外观与性状: 无色结晶,有樟脑样气味
危险标记: 14(有毒品)
用 途: 用于有机合成、医药等。也用作溶剂

2、对环境的影响

该物质对环境可能有危害,在地下水中有蓄积作用。在对人类重要食物链中,特别是在水生生物中发生生物蓄积。

一、健康危害

侵入途径:吸入、食入、经皮吸收。健康危害:本品对中枢神经系统有麻醉作用,对肝、肾有损害;对皮肤粘膜有轻度刺激作用。误服出现眩晕、呕吐、肝区痛、血中胆红素增高、心率减慢、肾炎及无尿。动物实验见软弱无力、嗜睡、步态不稳、后肢轻瘫;亦可见痉挛、心率加快、昏睡、腹泻、食欲减退等。

二、毒理学资料及环境行为

毒性:属低毒类。 急性毒性:LD504460mg/kg(大鼠经口);大鼠吸入57mg/L×8小时,致死。 亚急性和慢性毒性:大鼠经口1.5mg/kg/日×110日,肾功能异常;大鼠经口80mg/kg/日×110日,肝、肾细胞坏死,功能异常。 致突变性:Ames试验沙门氏菌株(五个菌种)+S9阴性。 致癌性:大鼠经口致肝瘤。

危险特性:高热时能分解出剧毒的光气。 燃烧(分解)产物:氯化氢、光气。

3、现场应急监测方法

4、实验室监测方法

气相色谱法《城市和工业废水中有机化合物分析》王克欧等编气相色谱法《固体废弃物试验分析评价手册》中国环境监测总站等译色谱-质谱法《水和废水标准检验法》19版译文,江苏省环境监测中心

5、环境标准
前西德(1982) 职业环境空气中最高容许浓度 10mg/m3
前苏联(1982) 地面水中最高容许浓度 0.01mg/L
前苏联(1975) 污水排放标准 2mg/L

6、应急处理处置方法 一、泄漏应急处理

隔离泄漏污染区,限制出入。建议应急处理人员戴自给式呼吸器,穿一般作业工作服。小量泄漏:用洁净的铲子收集于干燥、洁净、有盖的容器中。大量泄漏:收集、回收或运至废物处理场所处置。 废弃物处置方法:用焚烧法。废料同其它燃料混合后焚烧,燃烧要充分,防止生成光气。焚烧炉排气中的卤化氢通过酸洗涤器除去。

二、防护措施

呼吸系统防护:可能接触其粉尘时,应该佩戴自吸过滤式防尘口罩。紧急事态抢救或撤离时,建议佩戴自给式呼吸器。 眼睛防护:一般不需要特殊防护,高浓度接触时可戴安全防护眼镜。 身体防护:穿透气型防毒服。 手防护:戴防化学品手套。 其它:工作现场禁止吸烟、进食和饮水。工作毕,沐浴更衣。单独存放被毒物污染的衣服,洗后备用。注意个人清洁卫生。

三、急救措施

皮肤接触:脱去被污染的衣着,用肥皂水和清水彻底冲洗皮肤。 眼睛接触:提起眼睑,用流动清水或生理盐水冲洗。就医 吸入:迅速脱离现场至空气新鲜处。保持呼吸道通畅。如呼吸困难,给输氧。如呼吸停止,立即进行人工呼吸。就医。 食入:饮足量温水,催吐,洗胃。就医。

灭火方法:消防人员须佩戴防毒面具、穿全身消防服。喷水保持火场容器冷却,直至灭火结束。灭火剂:雾状水、泡沫、二氧化碳、砂土。

毒理学数据:

1.急性毒性LD50:4460mg/kg(大鼠经口)

2.刺激性 暂无资料

3.致突变性 姐妹染色单体交换:仓鼠卵巢330mg/L

4.致癌性 IARC致癌性评论:G2B,可疑人类致癌物。

生态学数据:

1.生态毒性

LC50:0.98mg/L(96h)(虹鳟鱼,动态);1.53mg/L(96h)(黑头呆鱼,动态);2.9mg/L(48h)(水蚤)

2.生物降解性

好氧生物降解(h):672~4320

厌氧生物降解(h):2688~17280

3.非生物降解性 暂无资料

4.其他有害作用 该物质对环境可能有危害,在地下水中有蓄积作用。在对人类重要食物链中,特别是在水生生物中发生生物蓄积。

CHEMICAL IDENTIFICATION

RTECS NUMBER :
KI4025000
CHEMICAL NAME :
Ethane, hexachloro-
CAS REGISTRY NUMBER :
67-72-1
BEILSTEIN REFERENCE NO. :
1740341
LAST UPDATED :
199712
DATA ITEMS CITED :
62
MOLECULAR FORMULA :
C2-Cl6
MOLECULAR WEIGHT :
236.72
WISWESSER LINE NOTATION :
GXGGXGGG

HEALTH HAZARD DATA

ACUTE TOXICITY DATA

TYPE OF TEST :
LD50 - Lethal dose, 50 percent kill
ROUTE OF EXPOSURE :
Oral
SPECIES OBSERVED :
Rodent - rat
DOSE/DURATION :
4460 mg/kg
TOXIC EFFECTS :
Details of toxic effects not reported other than lethal dose value
TYPE OF TEST :
LCLo - Lowest published lethal concentration
ROUTE OF EXPOSURE :
Inhalation
SPECIES OBSERVED :
Rodent - rat
DOSE/DURATION :
5900 ppm/8H
TOXIC EFFECTS :
Behavioral - muscle weakness
TYPE OF TEST :
LDLo - Lowest published lethal dose
ROUTE OF EXPOSURE :
Intraperitoneal
SPECIES OBSERVED :
Rodent - rat
DOSE/DURATION :
2900 mg/kg
TOXIC EFFECTS :
Details of toxic effects not reported other than lethal dose value
TYPE OF TEST :
LD50 - Lethal dose, 50 percent kill
ROUTE OF EXPOSURE :
Intraperitoneal
SPECIES OBSERVED :
Rodent - mouse
DOSE/DURATION :
4500 mg/kg
TOXIC EFFECTS :
Details of toxic effects not reported other than lethal dose value
TYPE OF TEST :
LDLo - Lowest published lethal dose
ROUTE OF EXPOSURE :
Intravenous
SPECIES OBSERVED :
Mammal - dog
DOSE/DURATION :
325 mg/kg
TOXIC EFFECTS :
Details of toxic effects not reported other than lethal dose value
TYPE OF TEST :
LD - Lethal dose
ROUTE OF EXPOSURE :
Oral
SPECIES OBSERVED :
Rodent - rabbit
DOSE/DURATION :
>1 gm/kg
TOXIC EFFECTS :
Details of toxic effects not reported other than lethal dose value
TYPE OF TEST :
LD50 - Lethal dose, 50 percent kill
ROUTE OF EXPOSURE :
Administration onto the skin
SPECIES OBSERVED :
Rodent - rabbit
DOSE/DURATION :
32 gm/kg
TOXIC EFFECTS :
Details of toxic effects not reported other than lethal dose value
TYPE OF TEST :
LDLo - Lowest published lethal dose
ROUTE OF EXPOSURE :
Subcutaneous
SPECIES OBSERVED :
Rodent - rabbit
DOSE/DURATION :
4 gm/kg
TOXIC EFFECTS :
Details of toxic effects not reported other than lethal dose value
TYPE OF TEST :
LD50 - Lethal dose, 50 percent kill
ROUTE OF EXPOSURE :
Oral
SPECIES OBSERVED :
Rodent - guinea pig
DOSE/DURATION :
4970 mg/kg
TOXIC EFFECTS :
Details of toxic effects not reported other than lethal dose value
TYPE OF TEST :
TDLo - Lowest published toxic dose
ROUTE OF EXPOSURE :
Oral
SPECIES OBSERVED :
Rodent - rat
DOSE/DURATION :
6944 mg/kg/16W-C
TOXIC EFFECTS :
Liver - changes in liver weight Kidney, Ureter, Bladder - changes in tubules (including acute renal failure, acute tubular necrosis) Kidney, Ureter, Bladder - changes in bladder weight
TYPE OF TEST :
TDLo - Lowest published toxic dose
ROUTE OF EXPOSURE :
Oral
SPECIES OBSERVED :
Rodent - rat
DOSE/DURATION :
9 gm/kg/16D-I
TOXIC EFFECTS :
Related to Chronic Data - death
TYPE OF TEST :
TDLo - Lowest published toxic dose
ROUTE OF EXPOSURE :
Oral
SPECIES OBSERVED :
Rodent - rat
DOSE/DURATION :
48750 mg/kg/13W-I
TOXIC EFFECTS :
Brain and Coverings - changes in brain weight Liver - changes in liver weight Kidney, Ureter, Bladder - changes in bladder weight
TYPE OF TEST :
TCLo - Lowest published toxic concentration
ROUTE OF EXPOSURE :
Inhalation
SPECIES OBSERVED :
Rodent - rat
DOSE/DURATION :
260 ppm/6H/6W-I
TOXIC EFFECTS :
Kidney, Ureter, Bladder - changes in bladder weight Endocrine - changes in spleen weight Related to Chronic Data - changes in testicular weight
TYPE OF TEST :
TDLo - Lowest published toxic dose
ROUTE OF EXPOSURE :
Oral
SPECIES OBSERVED :
Rodent - rabbit
DOSE/DURATION :
12 gm/kg/12D-C
TOXIC EFFECTS :
Liver - other changes Kidney, Ureter, Bladder - other changes Nutritional and Gross Metabolic - weight loss or decreased weight gain
TYPE OF TEST :
TCLo - Lowest published toxic concentration
ROUTE OF EXPOSURE :
Inhalation
SPECIES OBSERVED :
Rodent - guinea pig
DOSE/DURATION :
260 ppm/6H/6W-I
TOXIC EFFECTS :
Liver - changes in liver weight Related to Chronic Data - death
TYPE OF TEST :
TDLo - Lowest published toxic dose
ROUTE OF EXPOSURE :
Oral
SPECIES OBSERVED :
Rodent - rat
DOSE/DURATION :
10300 mg/kg/2Y-C
TOXIC EFFECTS :
Tumorigenic - Carcinogenic by RTECS criteria Liver - tumors
TYPE OF TEST :
TDLo - Lowest published toxic dose
ROUTE OF EXPOSURE :
Oral
SPECIES OBSERVED :
Rodent - mouse
DOSE/DURATION :
230 gm/kg/78W-I
TOXIC EFFECTS :
Tumorigenic - Carcinogenic by RTECS criteria Liver - tumors
TYPE OF TEST :
TD - Toxic dose (other than lowest)
ROUTE OF EXPOSURE :
Oral
SPECIES OBSERVED :
Rodent - mouse
DOSE/DURATION :
460 gm/kg/78W-I
TOXIC EFFECTS :
Tumorigenic - Carcinogenic by RTECS criteria Liver - tumors
TYPE OF TEST :
TDLo - Lowest published toxic dose
ROUTE OF EXPOSURE :
Oral
DOSE :
5500 mg/kg
SEX/DURATION :
female 6-16 day(s) after conception
TOXIC EFFECTS :
Reproductive - Fertility - litter size (e.g. # fetuses per litter; measured before birth) Reproductive - Fertility - other measures of fertility
TYPE OF TEST :
Mutation test systems - not otherwise specified

MUTATION DATA

TYPE OF TEST :
Sister chromatid exchange
TEST SYSTEM :
Rodent - hamster Ovary
REFERENCE :
EMMUEG Environmental and Molecular Mutagenesis. (Alan R. Liss, Inc., 41 E. 11th St., New York, NY 10003) V.10- 1987- Volume(issue)/page/year: 10(Suppl 10),1,1987 *** REVIEWS *** ACGIH TLV-Animal carcinogen DTLVS* The Threshold Limit Values (TLVs) and Biological Exposure Indices (BEIs) booklet issues by American Conference of Governmental Industrial Hygienists (ACGIH), Cincinnati, OH, 1996 Volume(issue)/page/year: TLV/BEI,1997 ACGIH TLV-TWA 9.7 mg/m3 (1 ppm) (skin) DTLVS* The Threshold Limit Values (TLVs) and Biological Exposure Indices (BEIs) booklet issues by American Conference of Governmental Industrial Hygienists (ACGIH), Cincinnati, OH, 1996 Volume(issue)/page/year: TLV/BEI,1997 IARC Cancer Review:Animal Limited Evidence IMEMDT IARC Monographs on the Evaluation of Carcinogenic Risk of Chemicals to Man. (WHO Publications Centre USA, 49 Sheridan Ave., Albany, NY 12210) V.1- 1972- Volume(issue)/page/year: 20,467,1979 IARC Cancer Review:Human No Adequate Data IMEMDT IARC Monographs on the Evaluation of Carcinogenic Risk of Chemicals to Man. (WHO Publications Centre USA, 49 Sheridan Ave., Albany, NY 12210) V.1- 1972- Volume(issue)/page/year: 20,467,1979 IARC Cancer Review:Group 3 IMSUDL IARC Monographs, Supplement. (WHO Publications Centre USA, 49 Sheridan Ave., Albany, NY 12210) No.1- 1979- Volume(issue)/page/year: 7,56,1987 TOXICOLOGY REVIEW AIHAAP American Industrial Hygiene Association Journal. (AIHA, 475 Wolf Ledges Pkwy., Akron, OH 44311) V.19- 1958- Volume(issue)/page/year: 40(3),A46,1979 *** U.S. STANDARDS AND REGULATIONS *** MSHA STANDARD-air:TWA 1 ppm (10 mg/m3) (skin) DTLVS* The Threshold Limit Values (TLVs) and Biological Exposure Indices (BEIs) booklet issues by American Conference of Governmental Industrial Hygienists (ACGIH), Cincinnati, OH, 1996 Volume(issue)/page/year: 3,124,1971 OSHA PEL (Gen Indu):8H TWA 1 ppm (10 mg/m3) (skin) CFRGBR Code of Federal Regulations. (U.S. Government Printing Office, Supt. of Documents, Washington, DC 20402) Volume(issue)/page/year: 29,1910.1000,1994 OSHA PEL (Construc):8H TWA 1 ppm (10 mg/m3) (skin) CFRGBR Code of Federal Regulations. (U.S. Government Printing Office, Supt. of Documents, Washington, DC 20402) Volume(issue)/page/year: 29,1926.55,1994 OSHA PEL (Shipyard):8H TWA 1 ppm (10 mg/m3) (skin) CFRGBR Code of Federal Regulations. (U.S. Government Printing Office, Supt. of Documents, Washington, DC 20402) Volume(issue)/page/year: 29,1915.1000,1993 OSHA PEL (Fed Cont):8H TWA 1 ppm (10 mg/m3) (skin) CFRGBR Code of Federal Regulations. (U.S. Government Printing Office, Supt. of Documents, Washington, DC 20402) Volume(issue)/page/year: 41,50-204.50,1994 *** OCCUPATIONAL EXPOSURE LIMITS *** OEL-AUSTRALIA:TWA 10 ppm (100 mg/m3) JAN 1993 OEL-BELGIUM:TWA 1 ppm (9.7 mg/m3) JAN 1993 OEL-DENMARK:TWA 1 ppm (10 mg/m3);Skin JAN 1993 OEL-FINLAND:TWA 1 ppm (10 mg/m3);STEL 3 ppm (30 mg/m3);Skin JAN 1993 OEL-FRANCE:TWA 10 ppm (100 mg/m3) JAN 1993 OEL-GERMANY:TWA 1 ppm (10 mg/m3) JAN 1993 OEL-THE NETHERLANDS:TWA 1 ppm (10 mg/m3);Skin JAN 1993 OEL-THE PHILIPPINES:TWA 1 ppm (10 mg/m3);Skin JAN 1993 OEL-SWITZERLAND:TWA 1 ppm (10 mg/m3);Skin JAN 1993 OEL-UNITED KINGDOM:TWA 5 mg/m3 (resp. dust) JAN 1993 OEL-UNITED KINGDOM:TWA 5 ppm (50 mg/m3) (vapor) JAN 1993 OEL IN BULGARIA, COLOMBIA, JORDAN, KOREA check ACGIH TLV OEL IN NEW ZEALAND, SINGAPORE, VIETNAM check ACGIH TLV *** NIOSH STANDARDS DEVELOPMENT AND SURVEILLANCE DATA *** NIOSH RECOMMENDED EXPOSURE LEVEL (REL) : NIOSH REL TO HEXACHLOROETHANE-air:8H CA TWA 1 ppm REFERENCE : NIOSH* National Institute for Occupational Safety and Health, U.S. Dept. of Health, Education, and Welfare, Reports and Memoranda. Volume(issue)/page/year: DHHS #92-100,1992 NIOSH OCCUPATIONAL EXPOSURE SURVEY DATA : NOHS - National Occupational Hazard Survey (1974) NOHS Hazard Code - 17385 No. of Facilities: 219 (estimated) No. of Industries: 5 No. of Occupations: 9 No. of Employees: 1488 (estimated) NOES - National Occupational Exposure Survey (1983) NOES Hazard Code - 17385 No. of Facilities: 170 (estimated) No. of Industries: 12 No. of Occupations: 23 No. of Employees: 8516 (estimated) No. of Female Employees: 576 (estimated)

符号 GHS07 GHS08 GHS09
GHS07, GHS08, GHS09
信号词 Warning
危害声明 H315-H319-H335-H351-H410
警示性声明 P261-P273-P281-P305 + P351 + P338-P501
个人防护装备 Eyeshields;full-face particle respirator type N100 (US);Gloves;respirator cartridge type N100 (US);type P1 (EN143) respirator filter;type P3 (EN 143) respirator cartridges
危害码 (欧洲) Xn:Harmful
风险声明 (欧洲) R36/37/38;R40;R51/53
安全声明 (欧洲) S36/37-S61-S45-S36/37/39-S26-S24-S16-S7
危险品运输编码 UN 9037
WGK德国 3
RTECS号 KI4025000
包装等级 III
危险类别 9
海关编码 2942000000

1.由四氯乙烷经氯化而得。将脱水后的四氯乙烷投入搪玻离反应锅,在强光照射下通入氯气,反应温度逐渐上升,最后保持在90-100℃。当反应液由浑转清,通氯管出现结晶时,氯化即到达终点。停止通氯,提高温度至120℃,排出锅内余氯到达终点。停止通氯,提出高温度至120℃,排出锅内余氯。出料至盛有沸水的结晶锅内,用热水洗涤,再加1%碳酸钠和5%尿素溶液搅拌除氯。用水充分洗涤后后冷却结晶,离心过滤,最后将结晶浸泡于蒸馏水中再甩干,于40℃干燥、粉碎即得六氯乙烷。工业上也采用三氯乙烯与氯气进行光氯化。三氯乙烯与氯气发生光氯化反应生成五氯乙烷,再与液碱作用生成四氯乙烯。四氯乙烯与液氯(1:0.213)经光氯化反应制得粗制品,再经纯碱液中和、水洗、冷却结晶、离心过滤、干燥,粉碎而得成品。用此法生产六氯乙烷,每吨产品消耗三氯乙烯680kg,液氯700kg。另外,四氯化碳在氯化铝存在下与氯气反应,或乙烯在300-350℃,与氯反应都可制得该品。

海关编码 2942000000