As weed-killers

A great number of various substituted aminophenyl derivatives of thiazolium, and their organic or metallic complexes, have been patented as weed-killers or regulating growth factors of plants (135-138). 

The new and highly specialized petroleum products used as weed killers represent an application to agriculture of products developed by modem petroleum technology. Their increased usage is certain as these herbicides replace more costly means for weed control, in some cases reducing the cost to about one third that of previously known methods. 

Chlorate salts are used as weed-killers and as strong oxidizing agents. Potassium chlorate, for example, is an oxidizer in matches, fireworks, and explosives. It also reacts vigorously with organic matter. 

Chlorate salts, such as KCIO3, are also strong oxidizing agents and are used as weed killers and as oxidizers in fireworks (see Chapter 12) and explosives. 

Other applications were herbicides, primarily sodium arsenate, as weed killers for railroad and telephone posts, desiccators, mainly arsenic acid (H3ASO4), for example, to facilitate mechanical cotton harvesting and for tobacco and blueberry fields. Most of these compounds, their derivatives or decomposition products are still present in various regions and contribute significantly to the arsenic burden of soils and waters. 

Herbicides are used to kill plants. Sodium chlorate, NaC103 and sodium arsenite, Na3As03, were commonly used as weed killers in the first half of the twentieth century, but inorganic arsenic compounds, in particular, are toxic to mammals. Organic herbicides are now used. They are much more toxic to certain types of plants than to others, so they can be used as selective weedkillers. Atrazine, which is a member of a class of herbicides called the triazines, is widely used to kill weeds in cornfields. The triazines contain six-membered rings with alternating carbon and nitrogen atoms. The effects of atrazine on human health are not yet clear. 

Products and Uses Component in fungicide, as weed killer and herbicide. Precautions Toxic by swallowing and breathing. A strong irritant. Synonyms none found. 

The best way to prepare a comprehensive chemical list is to perform a comprehensive assessment of your facility. This means a department-by-department search for every chemical present. It includes cleaning supplies, such as bathroom and window cleaners grounds maintenance chemicals, such as weed killers and fertilizer vendor samples being used on a trial basis fuels paints as well as all chemicals used in your company s daily operations. 

Chlorates are used as weed killers and are occasionally encountered in toxicology cases, where they can cause methaemoglobinaemia and liver failure. They can be identified in gastric aspirates by their reaction with diphenylamine reagent to give a blue colour. 

The ultimate site of action of nitrophenols, when used as weed killers, is unknown, although presumably they act as uncouplers of mitochondrial phosphorylation (see Section 4.4). Blackman (1951) pointed out that when high concentrations are used, precipitation of cell proteins and the rupture of cell membrane are likely as well. 

In North America, calcium cyanamide is no longer used as fertiliser, but it has limited use in special agricultural appHcations for defoHants, fungicides, herbicides, and as a weed killer. The primary industrial use is as a chemical intermediate for the manufacture of calcium cyanide, hydrogen cyanamide solution, and dicyandiamide. Calcium cyanamide is also used to add nitrogen to steel. 

Acetylene and ethylene compete as a chemical raw material. Ethylene is generally more economical, resulting in declining use of acetylene as a raw material. Calcium carbide, a raw material for acetylene has other uses. Treated with nitrogen, it gives calcium cyanamide, valuable as a fertilizer and weed killer, and a raw material for the production of melamine, used ir ng some modern plastics. 

CaNCN is used as a direct application fertilizer, weed killer, and cotton defoliant it is also used for producing cyanamide, dicyandiamide and melamine plastics. Production formerly exceeded 1.3 million tonnes pa, but this has fallen considerably in the last few years, particularly in the USA where the use of CaNCN as a nitrogenous fertilizer has been replaced by other materials. In 1990 most of the world s supply was made in Japan, Gennany and Canada. 

Another interesting case is that of a manufacturer who recommended use of 2,4-D weed killer as a selective spray for control of weeds in young carrots. He had previously... 

Addition of ammonium chloride to a drum of weed-killer was suspected as the cause of a violent explosion (involving formation of ammonium chlorate) [1]. Mixtures, used for smoke compositions, are hazardous [2],... 

Ammonium thiocyanate is used as an ingredient in antibiotic preparations, pesticides, liquid rocket fuels, adhesives, and matches. It is also used in photographic processes, to improve the strength of silks, and as a weed killer. 

Thiocyanates are present in water primarily because of discharges from coal processing, extraction of gold and silver, and mining industries. Thiocyanates in soil result from direct application of weed killers and disposal of by-products from industrial processes. Less important sources include release from damaged or decaying tissues of certain plants such as mustard, kale, and cabbage. 

In many crops where weed killers are used, applications must be made with care or the crop being weeded may suffer. This takes some attention. Coffee showed characteristic injuries (22, 51) from applications of the weed killers 2,4-D, TCA, and CMU [3-(p-chlorophenyl)-l,l-dimethylurea]. On the other hand, as in other tree crops, further work on coffee proved that, if properly handled, weed sprays did not result in important permanent harm to the trees. Some of the most recent work has shown (22) that amine salts and butoxyethanol esters of 2,4-D caused less... 

In the past 10 years, chemical weed killers have replaced the machete and the hoe to a large extent in the tropics, especially in sugar cane fields. More than any other chemical, 2,4-D and its derivatives are used. Herbicides could also be used profitably to a greater extent in crops such as pineapple, rubber, rice, coffee, pastures, and lawns. Methods and chemicals used in Puerto Rico are described and results are compared with other areas. 

Mat r industries use phenolic materials in their manufacturing processes. Phenol is also used in the production of dmgs, weed killers, and synthetic resins. Phenol and its derivatives are present in the wastewaters of industries such as cooking, pulp mills, paint and dyes, wine distilleries, oil and gasoline, synthetic rabber, textiles, pharmaceuticals, solvent, manufacture of pesticides, paper, and wood etc. [1]. 

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