the reaction as carried out in a granulator , according to the instant invention , allows for several arrangements . fig1 and 2 suggest alternative ways of carrying out the solubilizing process . fig1 presents one embodiment of the invention . in accordance with the figure , an ammonium sulfate stream ( 1 ) or an ammonia stream ( 2 ), together with a sulfuric acid stream ( 3 ) and a water stream ( 4 ), are fed into ammonium bisulfate forming reactor ( 8 ). the heat generated in the reaction , in the case of using the ammonia stream ( 2 ) may eventually be used for product drying . in reactor ( 8 ), a solution of 60 to 80 weight percent concentration of ammonium bisulfate is obtained , which is fed to granulator ( 9 ), which is also receiving powdered rock ( 5 ). the solubilization reaction will take place in the granulator itself , for a residence time of 1 to 10 minutes , and at a temperature within the range of 30 ° to 90 ° c . a portion of the thus obtained product ( 14 ) is recycled to granulator ( 9 ), through a recycle stream ( 15 ), corresponding to a recycle ratio of between 0 . 5 and 3 . 0 ; this recycle ratio is defined as the mass ratio of stream ( 15 ) to the sum of the other streams fed to granulator ( 9 ). alternatively , a rock pulp stream ( 6 ), at a 45 to 85 weight percent solids concentration , that may or not proceed from a phosphate rock beneficiation step , may be fed to granulator ( 9 ), alone or together with the powdered rock stream ( 5 ). in the same way , a stream ( 7 ) of sulfuric acid or ammonium bisulfate solution , or still , ammonium bisulfate dissolved in sulfuric acid , can be fed to granulator ( 9 ), together with stream ( 10 ) of ammonium bisulfate solution . such a stream ( 7 ) of acidifying substance , as above described , may be subdivided into several streams ( 11 , 12 , 13 , etc . ), that will be partially fed along the length of granulator ( 9 ). thus , according to the present invention , in this first embodiment , two alternatives are possible , for the partial solubilization of phosphate rock in a granulator . in one alternative ( i ), ammonium bisulfate would react with the powdered rock . such an alternative could give rise to route ( a ) a further addition of an amount of ammonium bisulfate or sulfuric acid , or both , through stream ( 7 ), or route ( b ) no further addition of an acidifying substance . another alternative ( ii ) would comprise ammonium bisulfate reaction with rock pulp . in this case the above - mentioned routes ( a ) and ( b ) would also be possible . the mole ratio of ammonium sulfate ( as a pure salt or prepared from ammonia and sulfuric acid ) to sulfuric acid in reactor ( 8 ) may be the stoichiometric one , i . e ., 1 . 1 . there is a possibility , however , of using a mole ratio other than 1 , with the above - mentioned alternatives i and ii being modified in that case . in any event , it is important that in the reaction system ( comprised of a mixing reactor , a conveyor belt or a granulator ), the above - mentioned mole ratio be between 0 . 25 and 2 . 0 . fig2 presents another embodiment of the invention . according to this figure , phosphate rock pulp ( 1 ), proceeding from some phosphate rock beneficiation step , is directed , together with ammonium sulfate ( 2 ), that may or not proceed from an ammonium sulfate forming reactor , to mixing vessel ( 5 ). the slurry thus obtained is then sent to granulator ( 7 ), which also receives a sulfuric acid stream ( 4 ), which permits &# 34 ; in situ &# 34 ; formation of ammonium bisulfate , for rock solubilization . the solubilization reaction will take place in the granulator itself for a residence time of from 1 to 10 minutes and at a temperature between 30 ° and 90 ° c . part of product ( 9 ) is recycled to granulator ( 7 ), through a recycle stream ( 8 ), corresponding to a recycle ratio of between 0 . 5 and 3 . 0 . the ammonium sulfate employed in the process can be subdivided , a part thereof being directed to mixing vessel ( 5 ) and another part solubilized in sulfuric acid stream ( 4 ), being sent to granulator ( 7 ). stream ( 4 ) of sulfuric acid or ammonium sulfate plus sulfuric acid , can be subdivided into several streams ( 10 , 11 , 12 , etc .) that are partially fed along the granulator . the system further provides for powdered rock feed ( 3 ) together with rock pulp and ammonium sulfate ( 6 ) directly into granulator ( 7 ). accordingly , the instant invention process in the present embodiment , employs the following alternatives : i -- mixing of rock pulp ( 1 ) with the entire amount ammonium sulfate ( 2 ), so as to completely solubilize that compound and subsequent feeding of this mixture to granulator ( 7 ), where sulfuric acid ( 4 ) is added , for &# 34 ; in situ &# 34 ; formation of ammonium bisulfate . ii -- adding of a portion of the ammonium sulfate required , together with the sulfuric acid ( 4 ), allowing the total amount of water fed to the graulator to be reduced . iii -- feeding powdered rock ( 3 ), together with the rock pulp and ammonium sulfate ( 6 ) to granulator ( 7 ), with the resulting variations as predicted in the two preceding alternatives . lastly , a third embodiment of the invention comprises the reaction between ammonium bisulfate and phosphate rock in a mixing reactor or on a conveyor belt , to obtain a powdered product . such a reaction system is capable of the same variations as shown for the use of a granulator , with regard to the raw - material feeding modes . in the following , some examples will be presented , that merely illustrate , but do not limit the scope of the invention . in a laboratory bench unit , there was fed , through a peristaltic pump , 35 g / min of a pulp containing 45 . 8 % concentrate from patos de minas ( 23 . 1 % total p 2 o 5 ), 12 . 1 % dissolved ammonium sulfate and 42 . 1 % water , to a beaker , the above - mentioned composition having been blended with 3 . 2 g / min sulfuric acid at 96 % concentration , fed through a diaphragm metering pump , at a continuous rate , immediately prior to the dropping of the products into the container . average temperature was 60 ° c ., the product being cooled to room temperature . h + / p 2 o 5 mole ratio in the experiment was 2 . 4 . a product was obtained , which after drying in an oven , weighed 47 g and presented the following composition : 15 . 6 % total p 2 o 5 ; 14 . 2 % p 2 o 5 soluble in 2 % citric acid ( 1 : 100 ); 7 . 6 % water - soluble p 2 o 5 ( 1 : 250 ); 1 % moisture and 3 . 7 % total nitrogen . in a laboratory bench unit , there was fed , by means of a peristaltic pump , 37 g / min of a pulp comprised of 58 . 5 % patos de minas concentrate ( 23 . 1 % total p 2 o 5 ), 15 . 4 % dissolved ammonium sulfate and 26 . 1 % water , into a beaker , the above mixture having been blended with 7 . 4 g / min sulfuric acid at 96 % concentration added through a diaphragm metering pump , in a continuous mode , immediately before the dropping of the products into the container . average temperature was 85 ° c ., the product having been cooled and dried under ambient conditions . the h + / p 2 o 5 mole ratio in the experiment was 4 . 1 . the product , after drying , weighed 1 , 700 g and presented the following composition : 12 . 7 % total p 2 o 5 ; 12 . 5 % of 2 % citric acid - soluble p 2 o 5 ( 1 : 100 ); 10 . 6 % water - soluble p 2 o 5 ( 1 : 250 ); 12 . 2 % moisture and 3 % total nitrogen . in a laboratory bench unit , there was fed into a granulator , through a peristaltic pump , 22 . 9 % g / min of a pulp containing 30 % patos de minas concentrate ( 23 . 1 % total p 2 o 5 ), 27 % dissolved ammonium sulfate , and 43 % water . this stream was fed over a continuous bed of grains , charged into the granulator through a metering device , at a flow rate of 54 . 4 g / min . the above - mentioned granules had 16 . 7 % total p 2 o 5 , 8 . 3 % p 2 o 5 soluble in 2 % citric acid solution ( 1 : 100 ), 2 % moisture and 2 % total nitrogen . over the bed formed by the mixing of the pulp stream and the granule recycle stream , a stream at a flow rate of 9 . 5 g / min was sprayed , comprised of 69 . 5 % 100 % sulfuric acid , 28 . 3 % ammonium sulfate and 2 . 2 % water , which stream is fed through a metering diaphragm pump . h + / p 2 o 5 mole ratio , based on the recycle 2 % citric - acid - insoluble p 2 o 5 and on the p 2 o 5 of the rock , was equal to 3 . there was obtained 3 , 845 g of a product with 13 . 2 % total p 2 o 5 , 9 . 4 % of 2 % citric acid - soluble p 2 o 5 ( 1 : 100 ), 6 % water - soluble p 2 o 5 , 9 % moisture and 3 . 3 % total nitrogen . in a pilot plant , there was fed , through a screw conveyor and into a rotating drum type granulator , 74 kg recycle granules , with 18 . 3 % total p 2 o 5 , 9 . 2 % p 2 o 5 soluble in 2 % citric acid ( 1 : 100 ), 3 % moisture and 2 % total nitrogen . the above - mentioned granulator was also charged with a pulp comprised of 65 kg patos de minas concentrate ( 23 . 1 % total p 2 o 5 ), 15 kg ammonium sulfate and 23 kg water , through a centrifugal pump . the above - mentioned pulp and recycle material amounts were mixed during the operating time of the granulator and , during this period , 24 kg sulfuric acid at 96 % concentration was sprayed over the mass , providing a h + / p 2 o 5 mole ratio of 3 , at a temperature level of 45 ° c . 180 kg of a granulated product with a 16 . 5 % total p 2 o 5 content , 11 . 2 % p 2 o 5 soluble in 2 % citric acid ( 1 : 100 ), 7 . 7 % water - soluble p 2 o 5 ( 1 : 250 ), 2 . 9 % moisture and 2 . 6 % total nitrogen , was obtained . a product prepared in the pilot plant , in dry condition , containing 19 . 2 % total p 2 o 5 , 8 % p 2 o 5 soluble in 2 % citric acid ( 1 : 100 ), 2 . 5 % water - soluble p 2 o 5 ( 1 : 250 ) and 2 . 1 % total nitrogen was agriculturally evaluated , in two successive crops . the first one was a rice crop and the second one , for the evaluation of a residual effect , was a corn crop , which has a high demand for phosphorus . normal superphosphate was used as a basis for comparison , in the experiments . the samples studied for each crop were the following : 2 . cultivation with 150 ppm phosphorus , via pilot - plant produced fertilizer , with and without liming ; 3 . cultivation with 300 ppm phosphorus via pilot - plant produced fertilizer , with and without liming . 4 . cultivation with 225 ppm phosphorus , via normal superphosphate , with and without liming . in all of the samples , a balancing was made , of sulfur , potassium , nitrogen and micronutrients , in a &# 34 ; cerrado &# 34 ; soil . test results are to be found in tables i and ii . table i______________________________________starting crop - rice dry mattertreatment ( g / pot )* ______________________________________ ( 1 ) n , k , mg , s , micro 1 , 762 c ( 2 ) 1 + liming 2 , 376 b ( 3 ) 1 + 150 ppm p - fertilizer 2 , 604 b ( 4 ) 1 + 150 ppm p - fertilizer + liming 3 , 345 a ( 5 ) 1 + 300 ppm p - fertilizer 3 , 032 ab ( 6 ) 1 + 300 ppm p - fertilizer + liming 3 , 025 ab ( 7 ) 1 + 225 ppm p - simple superphosphate 2 , 885 ab ( 8 ) 1 + 225 ppm p - simple superphosphate + 2 , 785 ab liming______________________________________ * data followed by the same letters are not statistically different . table ii______________________________________second crop - corn ( maize ) dry mattertreatment ( g / pot )* ______________________________________ ( 1 ) n , k , mg , s , micro 2 . 008 b ( 2 ) 1 + liming 2 . 203 b ( 3 ) 1 + 150 ppm p - fertilizer 1 . 822 b ( 4 ) 1 + 150 ppm p - fertilizer + liming 2 . 356 b ( 5 ) 1 + 300 ppm p - fertilizer 1 . 879 b ( 6 ) 1 + 300 ppm p - fertilizer + liming 3 . 323 a ( 7 ) 1 + 225 ppm simple superphosphate 2 . 059 b ( 8 ) 1 + 225 ppm simple superphosphate + 3 . 214 a liming______________________________________ * data followed by the same letter are not statistically different .