CA1096191A

CA1096191A - Herbicidal compositions

Info

Publication number: CA1096191A
Application number: CA276,251A
Authority: CA
Inventors: George E. Davies; David M. Foulkes
Original assignee: Imperial Chemical Industries Ltd
Current assignee: Syngenta Ltd
Priority date: 1976-04-15
Filing date: 1977-04-15
Publication date: 1981-02-24
Also published as: EG12605A; IE44883L; TR19211A; GR61602B; DE2709307A1; FI58711B; FI771161A7; FI58711C; FR2347883A1; LU77128A1; NL7702758A; MY8000150A; SE7704238L; AU2414377A; IT1077294B; NL172115B; NO146563B; ES457860A1; NZ183410A; CH628208A5

Abstract

ABSTRACT
Herbicidal compositions comprising a herbicidal bipyridylium quaternary salt containing a triazolo [1,5-a] pyrimidine derivative; such compositions having an emetic effect if swallowed.

Description

`" 1096191 This invention relates to herbicidal compositions containing a herbicidal bipyridylium quaternary salt as an active ingredient.
Over the years, a wide range of pesticides has been S developed for agricultural use in the control of fungal and insect pests and weeds. While these substances are neces-sarily toxic to certain forms of life, when used wlth due care and in accordance with governmentally approved codes of practice, they present no hazard to human life t However, ln spite of efforts to encourage those concerned with pesti-cides to adopt safe handling practices, instances of misuse of pesticides do occur. One particular unsafe practice in the case of liquid pesticides is for an operator to transfer a small amount of the concentrated pesticide to a domestic container such as a beverage bottle for subsequent use at home. The risk attached to this practice is of course that child or incautious adult coming upon the bottle may swallow the contents with possibly serious consequences.
We have now found it possible to reduce the likelihood , - .
~ 20 of serious consequences of such accidental swallowing by - induction of emesis. This can result in some cases in the ,;
,~ ~ rapld removal of the pesticldal composition from the stomach ~ and digestive tract before lethal amounts of the pesticide . :
can be assimilated by the body.
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.: -,' ', 109619i We have further discovered that the admixture of a known triazolo ~I,S-~7 p~rimidine derivative of formula (I), as specified hereinafter, to a herbicidal bipyridylium quaternary salt in a herbicidal composition produces a composition which if swallowed tends to induce emesis, and thereby, expulsion of the composition According to the invention there is provided a herbicidal composition of reduced health hazard comprising a salt of a herbicidal bipyridylium quaternary cation and a s-tirazolo ~ ,5- ~ pyrimidine derivative of the formula:

R ~ ~ ~ ~HR
0~ ~
R2 (I) wherein Rl is hydrogen or n-propyl, R2 is n-propyl or allyl and R~ is methyl or n-pro~yl; or an acylated derivative thereof; or : a base addition salt thereof. The s-triazolo /1,5-a7pyrLmidine ~: ring structure is numbered as shown below:
. .
-~ 7 6 ~ N ~ N

. S ~ ~ ~ N

~ Particular derivatives of 5-oxo-4,5-dihydro-s-: tria~olo ~,5-~ pyrimidine of use in the practice of the invention are:-~096~9~

6-methyl-4-n-propyl-2-n-propylamino-2-amino-6-methyl-4-allyl-2-amino-4,6-di-n-propyl-2-ethoxycarbonylamino-6-methyl-4-n-propy}-An especially useful triazolo-pyrimidine for use in the compositions of the invention is 2-amino-6-methyl-5-oxo-4-n-propyl-4,5-dihydro-s-triazolo ~ l,S-a ~ pyr~midine (II).

C~3 ~ N ~ N

n-Pr (II) Preferred herbicidal bipyridylium quaternary salts for use in the compositions of the invention are those of the following formulae:-~: ~ n C X_7 n-;; \ ~
,~ CH2CH2 or .

R-N ~ _Rl 2 c X 7 n-:, , wherein R and Rl, which may be the same or different, stand .

- _ ,,~ _ 1096~91 for alkyl radicals of from 1 to 4 carbon atoms which may be substituted by hydroxyl, halogen, carboxyl, alkoxy, alkyl-carbonyl, alkoxycarbonyl, carbamoyl or N-substituted carbamoyl; ~X 7 n represents an anion and n is an integer from 1 to 4 inclusive.
Particularly preferred herbicidal bipyridylium quaternary salts are those listed below:-1,1-dimethyl-4,4'-bipyridylium dl(methylsulphate) (paraquat dimethosulphate) 1,1'-ethylene-2,2'-bipyridylium dibromide (diquat dibromide) 1,1'-dimethyl-4,4'-bipyridylium dichloride (paraquat dichloride) 1,1'-di-2-hydroxyethyl-4,4'-bipyridylium dichloride 1-(2-hydroxyethyl-1'-methyl)-4,4'-bipyridylium dichloride 1,1'-di-carbamoylmethyl-4,4'-bipyridylium dichloride :~ 1,1'-bis-N,N-dimethylcarbamoylmethyl-4,4'-bipyridylium .~ dichloride ~;~ 1,1'-dimethyl-4,4'-bipyridylium sulphate (paraquat sulphate) `~ 1,1'-bis-N,N-diethylcarbamoylmethyl-4,4'-bipyridylium dichloride 1,1'-diacetonyl-414'-blpyridylium dichloride .
1,1'-diethoxycarbonylmethyl-4,4'-bipyridylium dibromide The names in brac~ets alongside some of the compounds ~3961~1 in the above list are the accepted common names for these compounds. Thus 'paraquat' is the common name for the 1,1'-dimethyl-4,4'-bipyridylium cation. Paraquat is a particularly preferred bipyridylium cation for use in the compositions of the invention. A particularly preferred anion ~ X ~ n is the chloride anion, for reasons of convenience and economy, but any anion which gives rise to a conveniently water-soluble salt may be used if desired. The herbicidal action is due solely to the cation and for this reason the concen-tration of a herbicidal bipyridylium salt composition is :`
frequently given in terms of the cation alone. The amount of herbicidal bipyridylium quaternary salt present in the -~, compositions of the invention is generally from 1.0 to 99.9%
by weight.
The compositions of the invention may comprise a .
carrier or diluent, and may be solids, e.g. granules, or liquids, e.g. aqueous solutions.
In a preferred aspect the invention provides a concen-trated herbicldal composition comprising an aqueous solution of a salt o a herbicidal bipyridylium quaternary cation and a triazolo-pyrlmldlne as hereinbe~ore defined. Preerably `~ the herbicidal bipyridylium quaternary catlon is paraquat.
The amount of herbicidal bipyridylium quaternary cation present in the aqueous solution is preferably from 0.5 to 4.0 pounds per Imperial gallon tS0 grams to 400 grams per litre).

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Preferably the composition also comprises a surface active agent.
Surface-active agents may be cationic, non-ionic or anionic. Generally speaking cationic and non-ionic surface-active agents are preferred to anionic surface-active agents `
for use in the compositions of the invention, slnce the latter may interact undesirably with the bipyridylium quaternary salt in the compositions. Examples of non-ionic surface-active agents for use~ in the compositions of the invention include the condensation products of ethylene oxide with a}kyl phenols such as octylphenol, nonylphenol and octylcresol. Other non-ionic agents are the partial esters derived from long chain fatty acids and hexitol anhydrides, for example sorbitan monolaurate; the conden-sation products of the said partial esters with ethylene oxide; and the lecithins. Examples of cationic surface-active agents include quaternary salts and condensates of ethylene oxide with amines, for example the substances sold under the Trade Mark "Ethomeen", "Ethoduomeen", "Duoquad"
and "Arquad".
Particularly preferred surface-active agents are the combinations of surface-active agents described in U.K.
Patent No. 998,264 for use in formulations of herbicidal bipyridylium quaternary salts.
The preparation of the tria2010-pyrimidines (I) has _ ~_ ~96191 been described in U.K. Patent Specificatïon No ~1234635.
The emetic properties of the composition are primarily determined by the amount of triazolo-pyrimidine it contains.
In deciding the most appropriate amounts of triazolo-pyrimidine ~ 5 to use in any composition, regard must be had to the efficacy `'''~! of the triazolo-pyrimidine relative to the toxicity of the herbicide. The amount of triazolo-pyrimidine to be included is preferably such that any sample of the composition containing a potentially lethal dose of herbicide will ji 10 contain sufficient of the triazolo-pyrimidine to give it an ;....
emetic action. However, clearly neither lethal doses nor emetic doses can be direct}y measured in man; they can only be inferred from animal data.
i!; ~ Compositions according to the invention preferably contain from 0.1 to 5 parts by weight of the triazolo-~ pyrimidine (e.g. the triazolopyrimidine II) per 100 parts of ; the herbicidal bipyridylium quaternary cation (e.g. paraquat).
-~ Conveniently the amount of the triaæolo-pyrlmidine (e.g. the ; triazolopyrimidine II) used is 0.25 to 2.0 parts per 10 parts of herbicidal bipyrldylium quaternary cation ~e.g.
paraquat).
Concentrated aqueous formulations of the invention are corrosive. They must be handled with care, to avoid splashing of the eyes or skin, and they should not be allowed to come -- . . .
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into contact with corrodeable metals prior to dilution.
The compositions according to the invention may ~-also comprise coloured dyestuff or pigment compounds to give them a characteristic or distinguishing colour. Examples of such compounds are "Monastral Blue BNV Paste"* and "Lissamine Turquoise VN 150"*
The compositions according to the invention may also comprise a stenching agent. Examples of such stenching agents are: alkyl pyridines as described in U.K. Patent Specification ~o. 1406881; n-valeric acid; and tetrahydro-thiophen.
If desired, the triazolo-pyrimidines (I~ may be incorporated in thixotropic formulations of herbicidal quaternary salts. In particular the triazolo-pyrimidines (I) may be incorporated in the formulations of herbicidal bipyridylium quaternary salts described in our U.K. Patent Specification No. 1395502, These formulations comprise an aqueous solution of a herbicidal bipyridylium quaternary salt containing a gelling agent, for example finely divided silica, or a combination of the xanthan gum sold under the trade name "Kelzan" with sodium metaborate. Xanthan gum is a complex polysaccharide.
The compositions according to the invention may also comprise a herbicide other than a herbicidal bipyridylium ,~_ *denotes trade mark B ~

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~uaternary salt as hereinbefore defined. Examples of such herbicides are:

Amides (e.g. N,N-diallylchloroacetamide, 3,4-dichloropropion-anilide, N-(3-chloro-4-methyl-phenyl)-2-methylpentamide).

Carbamates (e.g. Isopropyl-N-phenylcarbamate, isopropyl-N-t3-chlorophenyl) carbamate, 4-chloro-2 but-2-ynyl-N-(3-chlorophenyl) carbamate, 2-chlorallyl-N,N-diethyl-dithio-; carbamate).

., Ureas/anilides (e.g. N,N'-di-(2,2,2-trichloro-1-hydroxy-ethyl)urea, 3,4-dichloroacetanilide, 0-chloroisobutyranilide, a-bromo-3,4-dichloroacetanilide, 3,4-dichloroformanilide, 2-- acetamido-3-chlorotoluene).

Diazines (e.g. 3,4,5,6-tetrahydro-3,5-dimethyl-2-thio-2H-1,3,5-thiadiazine, 5-bromo-3-isopropyl-6-methyluracil, 5-amino-4-chloro-2-phenyl-3-pyridazone, 1,2,3,6-tetrahydro-

3,6-dioxopyridazine).

Triazines (e.g. 2-chloro-4,6-bisethylamino-1,3,5-triazine, 2-chloro-4-ethylamino-6-isopropylamlno-1,3,5-triazine, 2-chloro-4,6-bisisopropylamlno-1,3,5-triazine, 4-ethylamino-6-isopropylamino-2-methoxy-1,3,5-triazine, 4,6-bisisopropyl-amino-2-methoxy-1,3,5-triazine).

/o _,~ _ 1096~l91 The inclusion of the triazolo-pyrimidine (I) in composi-tions according to the invention has no significant adverse effect upon the herbicidal activity of the compositions.
The invention is illustrated by the following Examples.

This Example illustrates a composition according to the invention which comprises 2-amino-6-methyl-5-oxo-4-n-propyi-4,5-dihydro-s-triazolo C 1,5-a ~ pyrimidine (II) in aqueous solution.

Ingredients % w/v Paraquat concentrate x (II) 0-05 Water to100 ml (where x gives 200 + 5 g/litre paraquat cation) Paraquat concentrate is a solution of paraquat dichloride containing 25% to 30% by weight of 1,1'-dimethyl-4,4'-bipyridylium catlon. The amount used was chosen to give a composition contalnlng 20% weight/volume paraquat cation.
The composition was prepared by simple agitation of the ingredients together.

_ ,~ _ ` 1096~1 This Example illustrates a composition according to the invention which comprises the triazolo-pyrimidine (II) in aqueous solution. The composition comprises the following ingredients.

Ingredients % w/v Paraquat concentrate x Sodium metaborate1.3 Sodium benzo~ate 2.0 Lissapol NX 1.1 DS 4392 ** 4.1 Silcolapse 5000*0.06 ~II) 0-05 r~ Water to 100 ml (where x gives 200 + 5 g/litre paraquat cation) "Lissapol" NX is a Trade Mark for a surface-active agent comprising a condensate of from 7 to 8 molar propor-tions of ethylene oxide with 1 molar proportion of ~-nonylphenol.
- ** DS 4392 is a code number for a surface-active agent 20 comprising a mixture of amines derived from soya bean fatty acids condensed with approximately 15 molar proportions of ethylene oxide.

*denotes trade mark.
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1~96191 "Silcolapse" is a Trade Mark for an anti-foaming agent comprlsing a silicone derivative.
The composition described above was prepared by simple agitation of the ingredients together.
.

This Example illustrates a composition according to the invention which comprises a gelling agent in addition to the triazolo-pyrimidine (II). The composition comprises the following ingredients.

Ingredients Amount in Grams Paraquat concentrate x "Kelzan" 0.4 (added as 1%
solution in water) Sodium metaborate 0.014 ~issapo} NX* 1.1 DS 4392 4.1 ~II) 0-05 Silcolapse 5000* 0.01 Water to 100 ml (where x gives 200 + 5 g/litre para~uat ion) The composition described above was prepared by simple agitation of the ingredients together and was sufficiently fluid when prepared to be poured into containers. On _~ _ B

~ 109619~

standing for 15 to 20 minutes the composition formed a gel and was not pourable unless vigorously shaken.

This Example illustrates a dry free flowing granular composition which is both stable in storage and is readily convertible into an aqueous solution for application as a spray.
A solution was made up having the following composition in which percentages are by weight.

Paraquat dichloride 33.0 2-amino-6-methyl-5-oxo-4-n-propyl-

4,5-dihydro-s-triazolo C 1,5-a~
pyrimidine (II) 0.1 ~ Sodium metaborate 2.5 `~ Potassium phosphate 1.6 Lissapol NX 24.0 Water 38.8 310 gms of the above solution were then added in a thin stream to 690 gms of dried magnesium sulphate contained in the bowl of a HOBART C.E. 100 dough mixex (''HOBARTI' is a Trade Mark). The resulting product which was dry was then '~ , _ ~ _ . -B

109619~

passed through a granulating machine and finally agitated in a sieve having 30 meshes per linear inch to remove dust.
The resulting granules had a size of at least 0.9 mm and possessed a solution rate of 150 seconds.

This Example illustrates a composition according to the invention which comprises 2-amino-6-methyl-5-oxo-4-_-propyl-4,5-dihydro-s-triazolo C 1,5-a ~ pyrimidine (II) and a stenching agent in aqueous solution.

Ingredients % w/v Paraquat concentrate x n-valeric acid 1.0 DS 4392 4.0 Silcolapse * 0.01 Lissapol NX* 1.0 Water to 100 mls (where x gives 200 g/l paraquat ion).

The composition described above was prepared by simple agitation of the ingredients together.

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1~96191 .

This Example illustrates a composition according to the invention which comprises 2-amino-6-methyl-5-oxo-4-n-propyl-4,5-dihydro-s-triazolo C 1,5-a~7 pyrimidine (II) in a thickened, coloured, aqueous solution.

Ingredients % w/v Paraquat concentrate x Synperonic 2 `* 2.5 Synperonic 16 * 2.5 Nansa 1106* 8.5 Monastral BNVS*Paste 1.0 Pyridine Base 1.0 Water to 100 mls (where x gives 200 g/l paraquat ion).
~, .
15"Synperonic" and "Nansa" are Trade Marks. Synperonic 2 is a condensation product of a mixture o~ 67~ C13 and 33 C aliphatic alcohols with two equivalents of ethylene oxide. Synperonic 16 ls a condensation product of a mixture of 67~ C13 and 33% C15 aliphatic alcohols with sixteen ; equivalents of ethylene oxide. Nansa 1106 is sodium dodecyl (substantially C12 straight chain) benzene sulphonate.
Monastral BNVS paste is a dispersion comprising 15~ w/v copper phthalocyanine pigment in water. Pyridine base is a mixture consisting substantially of alkyl pyridines.

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~96~9~

This Example illustrates a composition according to the invention which comprises 2-amino-6-methyl-5-oxo-4-n-propyl-4,5-dihydro-s-triazolo ~ 1,5-a~7 pyrimidine (II) in aqueous solution.

Ingredients % w/v diquat dibromide x sodium molybdate 0.18 potassium phosphate (as a mixture of dlpotassium hydrogen phosphate and potassium dihydrogen phosphate) 2.75 (II) 0 05 water to 100 ml (where x gives 1 0 + S g/l diquat ion).

; 15 Diquat ion is 1,1'-ethylene-2,2'-bipyridylium cation.
The composition described above was prepared by simple agitation of the ingredients together, and had a pH of 6.5 : 0.3.

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This Example illustrates a composition according to the invention which comprises 2-amino-6-methyl-5-oxo-4-n-propyl-4,5-dihydro-s-triazolo ~1,5-a ~ pyrimidine (II) in aqueous solution.

Ingredients % w/v Morfamquat dichloride x II .S
water to 100 mls (where x gives 300 + 5 g/l morfamquat ion).

Morfamquat ion is 1,1'-bis(3,5-dimethylmorphollno-carbonylmethyl)-4,4'-bipyridylium ion. The composition described above was prepared by simple agitation of the ingredients together.

This Example illustrates a compositlon according to the invention which comprises 2-amino-6-methyl-5-oxo-4-n-propyl-4,5-dihydro-s-triazolo C 1,5-a~7 pyrimidine (II) in aqueous solution.

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loa6lsl ' Ingredients % w/v l,l'-bis(diethylcarbamoylmethyl)-4,4'-bipyridylium dichloride x Tween 20 8 (II) 0 05 water to lO0 ml (where x gives 200 + 5 g/l l,l'-bis(diethylcarbamoylmethyl)-4,4'-bipyridylium ion). The composition described above was prepared by simple agitation of the ingredients together.
"Tween" is a Trade Mark. Tween 20 is a condensation product of one mole of sorbitan monolaurate with twenty moles of ethylene oxide.

EXAMP~E lO

This Example illustrates a composition according to the invention which comprises 2-n-propylamino-6-methyl-5-oxo-4-n-propyl-4,5-dihydro-s-triazolo C l,5-a;7 pyrimidine in aqueous solution.
,~ .
Ingredients % w/v .
; Paraquat concentrate x 2-n-propylamino-6-methyl-5-oxo-4-n-propyl-4,5-dihydro-s-triazolo ~1,5-a J pyrimidine 0.05 Water to lO0 ml (where x gives 200 + S g/litre paraquat cation) * denotes trade mark B

1~961~

ExAMæLE 11 This Example illustrates a composition according to the invention which comprises 2-amino-5-oxo-4,6-di-n-propyl-4,5-dihydro-s-triazolo ~1,5-a 7 pyrimidine in aqueous solution.

Ingredients % w/v Paraquat concentrate ~ x 2-amino-5-oxo-4,6-di-n-propyl-4,5-' dihydro-s-triazolo ~ l,S-a J -; pyrimidine 0.05 . Water to100 ml (where x gives 200 + 5 g/litre paraquat cation) . This Example illustrates a composition according to the invention which comprises 2-ethoxycarbonylamino-6-methyl-5-oxo-4-n-propyL-4,5-dihydro-s-triazolo ~1,5-a J pyrimidine in aqueous solution.

Ingredlents % w/v Paraquat concentrate x 2-ethoxycarbonylamino-6-methyl-5-oxo-4-n-propyl-4,5-dihydro-s-triazolo ~ l,5-a J pyrimidine 0.05 Water to lO0 ml (where x givos 200 + 5 g/litre paraquat cation) , - . . , :, . ... . ~
: - : - - .

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1~9619~

EXAMP~E 13 This Example illustrates a composition according to the invention which comprises 2-amino-6-methyl-5-oxo-4-allyl-4,5-dihydro-s-triazolo ~ 1,5-a ~ pyrimidine in aqueous solution.

Ingredients ~ w/v Paraquat concentrate x 2-amino-6-methyl-5-oxo-4-allyl-4,5-dihydro-s-triazolo C 1,5-a ~ -pyrimidine 0.05 : 10 Water to 100 ml (where x gives 200 + 5 g/litre paraquat cation) _ ~ _ ., .: -. :
.,, :
: .

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1 A herbicidal composition comprising a salt of a herbicidal bipyridylium quaternary cation and an emetically effective amount of an s-triazalo [1,5-a] pyrimidine deriv-ative of the formula:- wherein Rlis hydrogen or n-propyl, R2 is n-propyl or allyl and R3 is methyl or n-propyl; or an acylated derivative thereof; or a base addition salt thereof.

2. A composition as claimed in Claim 1, in which the salt of the herbicidal bipyridylium cation is a compound of the formula:- or wherein R and R1, which may be the same or different, stand for alkyl radicals of from 1 to 4 carbon atoms which may be substituted by hydroxyl, halogen, carboxyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, carbamoyl or N-substituted carbamoyl; [x] n- represents an anion and n is an integer from 1 to 4 inclusive.

3. A composition as claimed in Claim 1 or 2 in which the salt of the herbicidal bipyridylium quaternary cation is 1,1-dimethyl-4,4'-bipyridylium di(methylsulphate).

4. A composition as claimed in Claim 1 or 2 in which the salt of the herbicidal bipyridylium quaternary cation is 1,1'-ethylene-2,2'-bipyridylium dibromide.

5. A composition as claimed in Claim 1 or 2 in which the salt of the herbicidal bipyridylium quaternary cation is 1,1'-dimethyl-4,4'-bipyridylium dichloride.

6. A composition as claimed in Claim 1 or 2 in which the salt of the herbicidal bipyridylium quaternary cation is 1,1'-di-2-hydroxyethyl-4,4'-bipyridylium dichloride.

7. A composition as claimed in Claim 1 or 2 in which the salt of the herbicidal bipyridylium quaternary cation is 1-(2-hydroxyethyl-1'-methyl)-4,4'-bipyridylium dichloride.

8. A.oomposition as claimed in Claim 1 or 2 in which the salt of the herbicidal bipyridylium quaternary cation is 1, 1'-di-carbamoylmethyl-4,4'-bipyridylium dichloride.

9. A composition as claimed in Claim 1 or 2 in which the salt of the herbicidal bipyridylium quaternary cation is 1,1-bis-N,N-dimethylcarbamoylmethyl-4,4'-bipyridyllium dichloride.

10. A composition as claimed in Claim 1 or 2 in which the salt of the herbicidal bipyridylium quaternary cation is 1,1'-dimethyl-4,4'-bipyridylium sulphate.

11. A composition as claimed in Claim 1 or 2 in which the salt of the herbicidal bipyridylium quaternary cation is 1,1'-bis-N,N-diethylcarbamoylmethyl-4,4'-bipyridyllium dichloride.

12. A composition as claimed in Claim 1 or 2 in which the salt of the herbicidal bipyridylium quaternary cation is 1,1'-diacetonyl-4,4'-bipyridylium dichloride.

13. A composition as claimed in Claim 1 or 2 in which the salt of the herbicidal bipyridylium quaternary cation is 1,1'-diethoxycarbonylmethyl-4,4'-bipyridylium dibromide.

14. A composition as claimed in Claim 1 or 2 in which the s-triazolo [1,5-a] pyrimidine is 2-amino-6-methyl-5-oxo-4-n-propyl-4,5-dihydro-s-triazolo [1,5-a] pyrimidine.

15. A composition as claimed in Claim 1 or 2 in which the s-triazolo [1,5-a]pyrimidine is 6-methyl-5-oxo-4-n-propyl-2-n-propylamino-4,5-dihydro-s-triazolo [1,5-a]pyrimidine.

16. A composition as claimed in Claim 1 or 2 in which the s-triazolo [1,5-a]pyrimidine is 4-allyl-2-amino-6-methyl-5-oxo-4,5-dihydro-s-triazolo [1,5-a]pyrimidine.

17. A composition as claimed in Claim 1 or 2 in which the s-triazolo [1,5-a]pyrimidine is 2-amino-4,6-di-n-propyl-5-oxo-4,5-dihydro-s-triazolo [1,5-a]pyrimidine.

18. A composition as claimed in Claim 1 or 2 in which the s-triazolo [1,5-a]pyrimidine is 2-ethoxycarbonylamino-6-methyl-5-oxo-4-n-propyl-4,5-dihydro-s-triazolo [1,5-a]pyrimidine.

19. A composition as claimed in Claim 1 or 2 in which the s-triazolo [1,5-a]pyrimidine is 2-amino-6-methyl-5-oxo-4-n-propyl-4,5-di-hydro-s-triazol [1,5-a]pyrimidine in the amount of 0.1 to 5.0 parts per 100 parts of herbicidal bipyridylium quaternary cation.

20. A composition as claimed in Claim 1 or 2 in which the s-triazolo [1,5-a]pyrimidine is 2-amino-6-methyl-5-oxo-4-n-propyl-4,5-di-hydro-s-triazolo [1,5-a]pyrimidine in the amount of 0,25 to 2,0 parts per 100 parts of herbicidal bipyridylium quaternary cation.

21. A composition as claimed in Claim 1 or 2 which further comprises a carrier or diluent which carrier or diluent is a solid.

22. A composition as claimed in Claim 1 or 2 which further comprises a carrier or diluent which carrier or diluent is aqueous.

23. A composition as claimed in Claim 1 or 2 comprising a surface active agent.

24. A composition as claimed in Claim 1 or 2 comprising a stenching agent.

25. A composition as claimed in Claim 1 or 2 comprising a stenching agent which is an alkyl pyridine base.

26. A composition as claimed in Claim 1 or 2 comprising a coloured dyestuff or pigment compound.

27. A composition as claimed in Claim 1 or 2 which further comprises a carrier or diluent wherein the carrier or diluent is a gelling agent.

28. A composition as claimed in Claim 1 or 2 comprising any other hebicidal compound.

29. A herbicidal composition comprising an aqueous solution of a salt of a paraquat cation containing 50 to 400 grams per litre of the paraquat cation and from 0.1 to 5 parts by weight of 2-amino-6-methyl-5-oxo-4-n-propyl-4-,5-dihydro-s-triazolo [1,5-a]pyrimidine per 100 parts by weight paraquat cation.