the present invention is directed toward a vacuum controlled device that can produce hydrogen gas on demand , and under control of a vehicle &# 39 ; s throttle as needed , for injecting into the air intake of an internal combustion engine . the present invention can be used with virtually any internal combustion engine ( including diesel engines ) and finds applications in cars , trucks , boats , ships , locomotives , agricultural machines , military vehicles and other devices such as mobile power stations , generators and any other internal combustion engines using gasoline , diesel , natural gas , propane or any other fuel . turning to fig1 , a block diagram of an embodiment of the present invention is seen . the internal combustion engine 1 has an air intake 8 where flow into the air intake is controlled by a valve 6 that is coupled to the vehicle &# 39 ; s throttle linkage 9 , 10 . a parallel path of regular air ( not shown ) can optionally be supplied into the air intake at this point if desired . a reaction chamber 2 that can produce hydrogen in quantity and demand to vacuum can be located near the engine 1 . the air intake 8 can be connected through a hose 7 to the valve 6 . the reaction chamber 2 can be connected from its gas outlet 11 , through a hose 3 to a filter 4 . the filter 4 can be connected through a hose 5 to the valve 6 . an open inlet port 12 on the reaction chamber allows air to enter and be pulled through the chamber in response to the vacuum . the filter 4 is optional , but generally recommended to clean the hydrogen produced by a chemical reaction in the reaction chamber 2 . with no filter , liquid and other byproducts of the reaction might be drawn into the engine 1 . the filter 4 and chemical elements of the reaction chamber 2 are parts that can be replaced after a certain amount of usage . fig2 shows a schematic drawing of an embodiment of the reaction chamber 2 . the chamber 2 contains a quantity of liquid 13 that , under a no - vacuum condition , rests at a particular surface level measured vertically . a support 14 holds a piece or block of metal 15 on a platform just above the no - vacuum resting surface level of the liquid 13 , with bottom and side surfaces exposed . when vacuum is drawn in the main exit portal 11 caused by depressing the vehicle &# 39 ; s throttle , the liquid is pulled upward in the reaction chamber and into contact with the metal 15 . the more vacuum pulled , the more surface contact with the metal . since the liquid 13 in contact with the metal 15 produces hydrogen gas 16 , the amount of vacuum directly controls the rate of hydrogen production . a portal 12 open to the atmosphere allows some air to be drawn into the chamber 2 so that the mixture leaving the chamber 2 via the exit portal 11 contains air mixed with hydrogen . the open portal 12 is normally smaller in diameter than the exit portal 11 . the result is a system where engine vacuum under control of the throttle controls the rate of hydrogen injection into the engine . any combination of liquid / metal that produces hydrogen gas can be used in the chamber 2 ; however , the preferred liquid is a solution of sodium hydroxide , and the preferred metal is aluminum . sodium hydroxide ( lye ) can be considered a reactant or catalyst to make the liquid water react with the metal . other catalysts are not necessary with this particular combination . any liquid / metal combination that produces hydrogen gas , when the metal is in contact with the liquid , with or without an additional catalyst , is within the scope of the present invention . any catalyst of any type that enhances the reaction is also within the scope of the present invention ; however , as stated the lye / water combination generally does not need any other catalyst to react . the minimum requirement for a system is around one milliliter of liquid ( water ), around one milligram of metal ( aluminum ) and around one milligram of reactant ( naoh ). any other quantities or combinations may be used . in a typically automobile or vehicle use , the reaction chamber can be around 5 - 6 inches in diameter , contain from 1 to 4 liters of solution and contain a bar or block of metal of several grams up to several hundred grams . a preferred concentration of naoh in water is between 5 % to 15 %. it should be noted that the reaction described does not need extra heat and does not produce excessive heat itself . therefore , there is no need to externally cool the reaction . no electric current is required , and the solution is not excessively corrosive . even though the solution as described generally has a depressed freezing point over pure water , to prevent freezing on particularly cold days or in particularly cold climates , a small amount of alcohol or glycol can be added to the mixture without any adverse effect on the reaction . the rate that the metal is dissolved depends on usage including city or rural driving , speed driven , etc . a typical auto arrangement can generally last around 5000 miles or more . at that point , the liquid and metal can be refreshed , and the filter replaced . this can be done in conjunction with an oil change or other routine maintenance . any other replacement interval is within the scope of the present invention . as previously stated , when the driver applies throttle , the vehicle &# 39 ; s vacuum increases causing the surface of the liquid 13 in the chamber 2 to rise and contact the bottom and / or side surface of the metal 15 , and upon further rising , contact the sides and possibly even the top surface of the metal 15 . the height of the metal should be sufficient to create an increasing , approximately linear , increase of hydrogen production as the level rises . saturation will occur when the metal is completely submerged . this point should be chosen near full throttle depression . in a typical vehicle application , the height can be from several centimeters to even a lot more . the rate of liquid rise depends on the diameter of the chamber 2 as well as the amount of vacuum supplied above the liquid . automobile engines typically produce between 90 - 100 kpa of manifold pressure ( vacuum ). the chamber diameter and metal height can be chosen to produce the desired gas production gradient for a given engine or engine / vehicle class . generally , for the liquid to rise in response to decreasing air pressure on its top surface ( caused by increase vacuum above it ), the liquid must display a second surface to the atmosphere . this can be achieved using a u - shaped or an open balance tube 16 shown in fig3 , or any other arrangement that presents a second liquid surface to the atmosphere . this allows the liquid to flow up and down in direct response to increasing or decreasing vacuum . any method or arrangement that allows the liquid surface level to rise and fall in direct response to vacuum is within the scope of the present invention . the chamber can be made of any material that is not affected by the reactants ; the hosing can be standard rubber hose with the preferred reactants described . the filter 4 can be any filter that will remove reactant and other impurities from the gas . fiber filters as well as charcoal filters or any other filters can be used . the filter 4 must allow vacuum buildup , and allow sufficient air flow and gas to pass through . fig4 shows a graph of throttle depression or engagement and rate of hydrogen production for a typical embodiment of the present invention . it can be seen that the relationship is approximately linear until the block becomes completely submerged . the normal operating range should generally be chosen so that the block is not normally totally submerged . use of the present invention can result in a tremendous increase in gas mileage for vehicles with internal combustion engines and a tremendous increase in efficiency for other engines . with fuel injected vehicles , it may be necessary to adjust injector pulse width and / or ignition timing to achieve maximum efficiency with injected hydrogen . any system that adjusts injector pulse width and / or timing should preferably revert back to normal settings whenever no hydrogen is being produced ( say because of an expended or faulty hydrogen generation system ). an optional hydrogen sensor can sense this condition . several descriptions and illustrations have been presented to aid in understanding the present invention . one of skill in the art will realize that numerous changes and variations can be made without departing from the spirit of the invention . each of these changes and variations is within the scope of the present invention .