the improved granulated fatty alcohol sulphates of the invention are obtained by slowly drying under vacuum a material consisting essentially of fatty alcohol sulphate , having a total dry matter content between 62 wt % and 80 wt %, while solid mixing means are provided to mechanically mix the drying mixture during the drying process . the remaining 38 - 20 wt % of dry matter typically consists of a solvent or a mixture of solvents , unsulphated fatty alcohol ( 0 . 5 - 2 . 0 wt %), nacl ( 0 - 0 . 5 wt %) and na 2 so 4 ( 1 . 0 wt %). according to a preferred embodiment of the invention the solvent consists essentially of water . according to another preferred embodiment of the invention , the solvent is a mixture of water and an organic solvent . suitable organic solvents that can be used are , e . g ., ethanol , propanol , isopropanol , acetone , methyl ethyl ketone , polyethylene glycol or the like . according to another preferred embodiment of the invention , additives and components like co - surfactants or builders may be added to the product . suitable co - surfactants that can be used are anionic surfactants , e . g ., dodecyl benzene sulphonate and toluene sulphonate , nonionic surfactants , e . g ., ethoxylated fatty alcohols , and cationic surfactants , e . g ., quaternary amido compounds , and the like . as will be appreciated by the skilled person , the advantages of the invention are achieved by the combined effect of a slow drying , such as can be achieved by vacuum drying in rotary equipment , and mechanical mixing of the slurry / solid material during drying , which results in the granulation being effected during drying . in one preferred embodiment of the invention the vacuum is maintained at a level comprised between 5 and 60 mbar , absolute pressure . other vacuum levels can of course be used , but they may be needlessly deep , or may require too long drying times to be operated with high economic advantage and , therefore , are not preferred , but they of course are within the ambit of the invention . according to a specific preferred embodiment of the invention the process is carried out in a mixing chamber coupled to vacuum generating means . in one embodiment of the invention the mixing means comprise scraper blades moving near the walls of the mixing chamber . preferably -- but not limitatively -- the distance between the scraper blades and the wall is between 0 . 1 and 10 mm , and the scraper blades rotate at a speed between 10 and 150 rpm . the actual heating method is not essential to the invention , and any suitable heating method and apparatus can be employed . one convenient heating method , however , is that in which heat is supplied to the material to be dried by a heating jacket provided around the drying chamber . as will be apparent to the skilled person , the invention is not limited to any specific fatty alcohol sulphate . preferred fatty alcohols are the c 10 - c 22 alcohols , e . g . sodium lauryl sulphate . the arrangement shown in fig2 was used in this experiment . the product is transferred from a supply tank 1 , by using a pump 2 , to a mixer dryer , 4 . the heat required in the process is supplied by the heating medium 3 , introduced into the dryer . the whole process is carried out under sub - atmospheric pressure , which is maintained by the vacuum system 5 . a 300 liter horizontal , jacketed drying chamber with rotary mixing blades was filled with 60 kg of zoharpon las 70 , containing sodium salt of lauryl alcohol sulphate . the structural formula of zoharpon las 70 is roso 3 m , wherein r is alkyl c 12 - c 16 and m is na . steam was applied in the jacket and vacuuming was gradually increased until the moisture content of the product reached 1 %. the actual rate of drying is shown in fig1 in which the amount of water drawn from the sample is given as a function of time ( line a ). two peaks in the x - ray analysis ( cubα , 40 kv , 18 ma ), in the angle range 50 °& lt ; 2θ & lt ; 8 °, one at about 6 . 5 ° and the second at about 7 . 8 °. the particles obtained had a spherical form , as may be seen in fig3 and 4 . as may be seen from fig3 and 4 , the product obtained has a polycrystalline structure composed essentially of round particles having a smooth surface . the product was compared with a commercially available product ( texapon zhk , ex henkel ), which is a sodium lauryl sulphate having a density of 0 . 21 - 0 . 28 gr / cc , and which comprises a c 12 - c 18 alkyl , and the corresponding results are reported in table i below : table i______________________________________size ( μm ) zoharpon las np texapon zhk______________________________________ & gt ; 1000 17 . 28 % 0 . 1 % 850 - 1000 15 . 46 % 0 . 19 % 710 - 850 10 . 66 % 0 . 3 % 600 - 710 11 . 8 % 0 . 49 % 500 - 600 11 . 4 % 3 . 14 % 300 - 500 24 . 5 % 26 . 99 % 250 - 300 1 . 1 % 19 . 53 % 150 - 250 5 . 6 % 25 . 61 % 45 - 150 2 . 1 % 23 . 45 % & lt ; 45 0 . 1 % 0 . 2 % total : 100 . 00 % 100 . 00 % ______________________________________ example 1 was repeated , but 20 liters of isopropyl alcohol were added to 60 kg of zoharpon las 70 , before drying , and the two materials were mixed . the drying rate of the solution in said chamber is given in fig1 ( line b ), as in the previous example . the following experiment was carried out to compare the rate of dissolution of a product according to the invention with the commercially available product texapon zhk ( ex henkel ). the conditions and results were as follows : 3 wt % of the tested material were added to water at 20 ° c . and were stirred using a magnetic stirrer . the materials used were as in example 2 , and the time required to reach a dear solution was measured ______________________________________ dissolution time dissolution ratematerial min ! gr / gr water · min ! ______________________________________zoharpon las np 2 . 05 0 . 015texapon k12 5 . 0 0 . 006 ( granular ) ______________________________________ the following experiment was carried out to compare the bulk density of a product according to the invention with the commercially available product texapon zhk ( ex henkel ). the samples were compared under three stress ranges : no stress , low stress and high stress . the results obtained for the bulk density in g / lit are given in table ii . table ii______________________________________stress applied bulk density ( g / lit ) kg / cm ! zoharpon las np texapon zhk______________________________________no stress 696 2940 . 077 727 3190 . 4 739 347200 1320 1186999 1367 1186______________________________________ in order to compare the flowability of a product according to the invention with texapon zhk , the following shear test was conducted . the test was carried out using a bulk of particles introduced into a shear tester . the shear tester was used for the measurement of the angle of the wall friction ( φ &# 39 ;). the procedure used to measure the horizontal forces required sliding a sample of bulk solid under a given normal load across a piece of material . ## equ1 ## knowing tan φ &# 39 ;, it is possible to assess whether or not mass flow is possible in a particular set up . the consolidation force applied was in the range 0 . 43 to 20 kg . the actual force required for the shear was measured and subsequently used for calculating the consolidation stresses , as well as angle of internal friction , unconfined yield strength and major consolidation stress . the first set of tests was carried out when the consolidation time was equal to zero . the second test was done after 24 hours of consolidation under consolidation forces of 0 . 84 to 14 kg . from the results of these tests , the flow function , ff , has been calculated . the flow function is defined as the ratio of major consolidation stress ( w m ) to the unconfined yield strength ( w c ). wherein , &# 34 ; unconfined yield strength &# 34 ; is meant to indicate the major consolidation stress when the shear stress is equal to zero . the flow function is used to characterize solids according to the following regimes : ______________________________________ff & lt ; 2 non - flowable solids ( sticky ) 2 & lt ; ff & lt ; 4 cohesive ( flowable ) 4 & lt ; ff & lt ; 10 easy flowingff & gt ; 10 free flowing______________________________________ table iii______________________________________ flow function ffconsolidation consolidation zoharpon texaponforce kg ! time hr .! las np zhk______________________________________ 0 . 84 0 5 . 17 5 . 81 24 0 . 56 0 . 46 2 . 8 0 5 . 18 6 . 11 24 0 . 93 0 . 76 7 . 0 0 5 . 84 6 . 44 24 1 . 48 1 . 2614 . 0 0 8 . 32 8 . 18 24 2 . 48 1 . 88internal sheer angle 25 . 5 37 . 2______________________________________ the above descriptions and examples have been given for the purpose of illustration , and are not intended to limit the invention in any way . many modifications can be effected in the various starting materials , additives and process conditions , all without exceeding the scope of the invention .