medium 250 to communicate with its external environment fig2 a 21 e illustrates the sequence of operations its sole control mechanism resides in the movements of the thermal response latch assembly 213 in a preferred embodiment the medium 600 will be a dishwashing detergent and the device will go through a hot cold and hot cycle before the medium 600 is dispensed fig2 a depicts a thermal response latch assembly 213 in the first phase of the sequence the external environment in this phase is cold and the bimetallic spring 200 is contracted located between the two ratchets 218 and its pivot 208 is in the fully down position as the temperature rises the bimetallic spring 200 starts to expand bow and push the ratchet 218 forward as the ratchet 218 is being pushed forward the latch 204 is simultaneously being pushed forward because it is an integral part of the latch notch assembly 213 when the external environment reaches its maximum temperature the bimetallic spring 200 is fully expanded and pushes the ratchet 218 to its farthest position forward this is depicted in fig2 b phase two begins when the temperature of the external environment begins to decrease the decrease in temperature causes the bimetallic spring 200 to contract pull back and ride up on the incline of the ratchet 214 until the spring 200 reaches the peak of the ratchet 203 at nearly full contraction the spring 200 drops down into the second ratchet notch 202 the ability of the spring 200 to ride up the ratchet incline 214.