olefinic hydrocarbon radicals of component b and can be any platinum containing catalyst component for example component d can be platinum metal a carrier such as silica gel or powdered charcoal bearing platinum metal or a compound or complex of a platinum metal a typical platinum containing catalyst component in the organopolysiloxane compositions of this invention is any form of chloroplatinic acid such as for example the readily available hexahydrate form or the anhydrous form because of its easy dispensability in organosiloxane systems a particularly useful form of chloroplatinic acid is that composition obtained when it is reacted with an aliphatically unsaturated organosilicon compound such as divinyltetramethyldisiloxane as disclosed by u s pat no 3 419 593 incorporated herein by reference the amount of platinum containing catalyst component that is used in the compositions of this invention is not narrowly limited as long as there is a sufficient amount to accelerate a room temperature reaction between the silicon bonded hydrogen atoms of component c with the silicon bonded olefinic hydrocarbon radicals of component b the exact necessary amount of said catalyst component will depend upon the particular catalyst and is not easily predictable however for chloroplatinic acid said amount can be as low as one part by weight of platinum for every one million parts by weight of organosilicon components b plus c preferably said amount is at least 10 parts by weight on the same basis.