INTERNATIONAL STANDARD I NTERNATIONAL ORGANIZATION FOR STANDARDIZATION M%K~YH uO~HAI I OPrAHH3AUMR n0 CTAH~APTM3AUMM~ORGANISATION INTERNATIONALE DE NORMALISATION Glass hydrometers Conventional value f[.]
INTERNATIONAL STANDARD INTERNATIONAL ORGANIZATION FOR STANDARDIZATION M%K~YH.uO~HAII OPrAHH3AUMR n0 CTAH~APTM3AUMM~ORGANISATION INTERNATIONALE DE NORMALISATION Glass hydrometers - Conventional value for the thermal cubic expansion coefficient (for use in the preparation of measurement tables for liquids) ArbomBtresen verre - Valeur cqnventionnelle pour la dilatabilite volumique thermique (ciutiliser lors de I’e’tablissementdes tables de mesuragedes liquides) First edition - 975-09-01 Ref No IS0 768-1 975 (E) UDC 542.3 : 531 754.3 : 53.081 Descriptors : laboratory glassware, hydrometers, thermal expansion Price based on pages F OR E WOR D I S0 of (th e I n tern ati on al n ati on al I n tern ati on al Me m be r u p h as th e Draft ri gh t Pri or to I S0 ou t be represen ted Stan d ard s by th e 972, Bod i es on I S0 th e resu l ts i nto of I n tern ati on al l SO/TC 48 h as for tran sformati on Re co mmen d at i o n Recommen d at i on cou n tri es revi ewed R 76 was Commi tt ees now part in of th i s Reco mme n d at i on I n tern ati on al to wh i ch approved by th e R 768 Stan d ard I S0 th e M e m be r fou n d it th erefore i den ti cal Bod i es Th l an d I srael Tu rkey Rep of ’ I tal y U n i ted U S A N e w Zeal an d Yu g osl avi a Peru Gre ece Pol an d expressed Bo d y di sapproval d i sapproved of th e of th e th e for Stan dardi zati on , Rep of Ki n g d o m Re commen d at i on tran sformati on Stan d ard Org an i zati on Afri ca, N eth erl an d s Ge rm an y Swi tzerl an d bei n g : I rel an d in of Tech n i cal an d 76 i t i s tech n i cal l y Can ad a I n tern ati on al were pu bl i sh ed process, Col ombi a M e m be r I n tern ati on al process Spai n I n tern ati on al i n th e work are ci rcu l ated as Sou th Bo d y org an i zati on s, Commi tt ees I ran Arab Every h as bee n set part I n di a N o M e m be r Pri n ted al so take Bel g i u m Fran ce I S0 are As R 768- 970 Cz ech osl ovaki a No Commi ttees Au stri a Eg ypt, d evel opi n g Commi t tee acceptan ce of th e Tech n i cal Stan d ard s su i tabl e I S0 th ei r federati on of I n tern ati on al I SO, Tech n i cal d ocu men t s Commi t tee fol l owi n g th e before th e work th ese tech n i cal l y repl aces I S0 by approval wi th work Tech n i cal a Tech n i cal Commi ttee i n l i son Th e Cou n ci l Recommen d ati on s; tran sformed I S0 wh i ch th at i s a worl d wi d e Bodi es) th rou g h for ad opted for Stan dardi zati on ) M e m be r i n a su bj ect an d n on - g overn men tal , M e m be r Stan d ard s as to for ( I S0 i s carri ed i n terested I n tern ati on al th e i nsti tu tes Stan d ard s Bod y g overn men tal to Org an i zati on stan d ard s 975 l of I SO/R 76 i n to an INTERNATIONAL STANDARD IS0 768-1 975 (E) Glass hydrometers - Conventional value for the thermal cubic expansion coefficient (for use in the preparation of measurement tables for liquids) SCOPE AND FIELD OF APPLICATION This International Standard specifies, for use in the of measurement tables for liquids, a preparation conventional value for the thermal cubic expansion coefficient of glass hydrometers It states how the indications of hydrometers having a ‘thermal cubic expansion coefficient differing from the recommended conventional value may be corrected for use in connection with measurement tables-in the construction of which the conventional value has been used coefficient of 0,000 025/“C the USE OF THE TABLES HYDROMETERS HAVING EXPANSION COEFFICIENT 0,000 025/k 5.1 APPLICABILITY IN ASSOCIATION A THERMAL DIFFERENT CONVENTIONAL VALUE OF COEFFICIENT INDICATION OF COEFFICIENT USED 4.1 The thermal cubic expansion coefficient hydrometers, namely 0,000 025/“C, used construction of measurement tables for liquids stated in the tables WITH CUBI C FROM b) the indication (I?‘) at “C of a hydrometer having the thermal expansion y/OC, but otherwise similar, is given by R=R’[1 +(0,000025-$(8-t)] Consequently, before using measurement tables in the construction of which the coefficient 0,000 025pC has been used, the hydrometer indication R’ at “C shall be modified to R’ [ + (0,000 025 - y) (0 - t)] It is apparent that multiplying it by R’ may be modified either by (0 - t) or by adding to it It is recommended that when preparing measurement tables for liquids the thermal cubic expansion coefficient of glass hydrometers should be taken to be 0,000 025/“C from between + (0,000 025 -7) differs a) the indication (R) at “C of a hydrometer of which the standard temperature is t “C and the thermal expansion is equal to the conventional value 0,000 025PC, and OF COEFFICIENT Measurement tables for liquids provide means for deriving, from the indications of density and/or relative density hydrometers at various temperatures, the corresponding value of the density and/or relative density with respect to water of the liquid at a reference temperature In principle such measurement tables must take account of the thermal expansion of the hydrometers Since hydrometers are made of various glasses, their expansion coefficients differ Consequently, it is desirable to use a single, conventional thermal cubic expansion coefficient in the construction of measurement tables and to associate with the tables information on how to adjust appropriately to the tables the indication of a hydrometer having any other thermal cubic expansion coefficient used General The relationship hvdrometers of the in the shall be 4.2 It shall be indicated in the measurement tables that hydrometer readings may have to be modified preparatory to using the tables if the thermal cubic expansion R’ (0,000 025 - y) (0 - t) 5.2 Applicability to density hydrometers Assuming that t ‘C is 20°C, the preferred standard temperature of density hydrometers complying with ISO/R 649, Density hydrometers for general purposes, R’ may be modified either by multiplying it by + (0,000 025 - 7) (6 - 20) or by adding to it R’ (0,000 025 - y) (0 - 20) If t “C is “C or 27 ‘C, the other recommended standard temperatures, these values shall be substituted for 20 “C ISO1 768-1 975 (E) TABLE Values of R’ (0,000 025 -7) Unit (0 - t) when : 0,001 Value It follows by (0 - rl = g/ml 5.3 01 0,000 025 -7) 01 0,000 ‘3.6 0,006 0,009 0.7 0,007 0,01 05 0,01 0.6 0,008 0,01 0,01 0.9 0,009 0,01 35 0,01 0,01 0,01 0,020 1 0,01 0,01 65 0,022 0,01 0,01 0,024 Applicability 020 to relative density 60/60 “F hydrometers + (0,000 025-y); (0 -601 where ti OF is the temperature of the liquid represents the expansion per degree Celsius and y still (8 - 60) or by adding to it R' (0,000 025-y) 0,01 When relative density 60/6O”F hydrometers are used, it is usual to express the temperature of the liquid in degrees Fahrenheit The modification formula quoted in 5.1 then becomes R'[l either by multiplying + (0,000 025-y): of (0,000 R’ 0,000 that R’ may be modified $9 TABLE Values of R’ (0,000 025 - y) (0 - 60) when (8 - 60) = and is expressed Unit : 0,001 -60) in degrees relative Value Fahrenheit density of (0,000 025 - 7) R’ 0,000 01 0,000 01 0,000 020 0.6 0.0033 0.0050 0,0067 0.7 0,0039 0.0058 0.0078 ‘33 0.0044 0.0067 0,0089 03 0.0050 0.0075 0,01 00 0,0056 0.0083 0,Olll 1 0.0061 0,0092 0.01 22 0,0067 0.01 00 0.01 33 it