TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Composition: In the composition of a metal nanoparticle, a primary particle diameter is less than or equal to 30 nm as measured using a transmission electron microscope. The particle is dispersed and is composed mainly of water. The electrical conductivity of the composition is not less than 1 S/m. The composition contains nitric acid component ( greater than or equal to 0.2 mass%); an aqueous resin dispersion; a water soluble resin; and a resin having an amine as a constitutional unit. Preferred Components: The metal species of the metal nanoparticle is silver.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The organic carboxylic acid having a carbon number of 3-8 or its derivative is present around a primary particle. EXAMPLE - A raw material solution A was prepared by mixing ion-exchanged water (68.6 g) with 28 mass% ammonia water (17.2 g) and heptanoic acid (20.7 g). A raw material solution B was prepared by diluting 80 mass% water-containing hydrazine (23.8 g) with ion-exchanged water (55.3 g). As a raw material solution C, a solution was prepared by dissolving silver nitrate crystal (79.8 g) in ion-exchanged water (68.6 g) heated to 60 degrees C. A reaction vessel was charged with ion-exchanged water (534.5 g), and the raw material solutions A, B, C were added to the ion-exchanged water to initiate the reaction under stirring. When the nd(2/3) was calculated for this reaction, it was 40. The temperature was maintained at 65 degrees C during reaction. The reaction was terminated 60 minutes after the initiation of the reaction. Afterwards, the reaction mixture was left still for 24 hours to concentrate the reaction product. After leaving the reaction mixture still for 24 hours, the supernatant of the above reaction product was removed, and the resultant concentrated product was poured into a capped bottle and left still for over one month to be further concentrated. Then the supernatant was removed to give a concentrated reaction product. The silver concentration in the concentrated reaction product was 64.1 mass%. The obtained concentrated reaction product (77.6 g) was separately placed in a beaker. The 19.6 g of the supernatant obtained in the precedent concentrating step was added to the concentrated reaction product. Then, 6% aqueous solution of hydroxyethyl cellulose (8.1 g) was added. Then the mixture of the obtained concentrated reaction, the supernatant, and the aqueous solution of hydroxyethyl cellulose was stirred and dispersed. Then, aqueous latex resin (3.5 g) and vinyl chloride copolymer (1.7 g), part of constitutional unit of which was neutralized by amine, was added. Again the mixture added with the aqueous latex resin and the vinyl chloride copolymer was stirred and dispersed. The amount of silver in the thus-obtained silver nanoparticle composition was 41.4 mass%. The average primary particle diameter was 9.2 nm, and the D50 diameter showing the 50% cumulative average diameter was 9.3 nm. The median diameter of the secondary aggregate of the composition was 0.3 mu m. The obtained composition was applied to a polyethylene terephthalate (PET) film. The obtained coating film was subjected to heat treatment at 140 degrees C for 30 seconds to form a sintered film. The surface resistivity measured was 1.9 Omega .