{"id":9392,"date":"2026-08-10T10:25:13","date_gmt":"2026-08-10T10:25:13","guid":{"rendered":"https:\/\/majistraleczacilari.org.tr\/?post_type=docs&p=1982"},"modified":"2026-08-21T11:48:14","modified_gmt":"2026-08-21T11:48:14","password":"","slug":"calculation-of-stock-solutions","status":"publish","type":"docs","link":"https:\/\/majistraleczacilari.org.tr\/en\/dokumanlar\/general-articles\/calculation-of-stock-solutions\/","title":{"rendered":"Calculation of Stock Solutions"},"content":{"rendered":"
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Calculation and dilution of stock solutions, scaling up (increasing) and scaling down (reducing) pharmaceutical formulas<\/strong><\/p>\n

Dear Colleagues, when preparing compounded formulas, accurate and complete calculation methods are undoubtedly of great importance for the efficacy of the formula.<\/p>\n

We should remember that a stock solution<\/strong> is the term given to the prepared solution form of an active substance. Such mixtures are prepared by dissolving that substance in an appropriate solvent.<\/p>\n

These preparations are mainly classified as:<\/p>\n

a) solid\/solid (weight\/weight = w\/w)<\/p>\n

b) solid\/liquid (weight\/volume = w\/v)<\/p>\n

c) liquid\/liquid (volume\/volume = v\/v)<\/p>\n

For example, in a formulation composed of two substances at a concentration of 3\/100 (w\/v), it should be understood that there are 3 g of substance in 100 ml of solution.<\/p>\n

CALCULATION OF STOCK SOLUTIONS<\/strong><\/p>\n

Examples;<\/p>\n

a) Preparation of 150 ml of glycerin\/rose water (eau de rose) solution at a concentration of 30% (v\/v):<\/p>\n

The formula requires the preparation of a 150 ml preparation containing 30% glycerin by volume.<\/p>\n

Rose water is added to 150×30\/100 = 45 ml of glycerin until it is completed to 150 ml.<\/p>\n

b) Preparation of 200 ml of salicylic acid\/ethanol (900<\/sup>) solution at a concentration of  5\/80 (w\/v):<\/p>\n

A preparation with a volume of 200 ml is required in the formula, and 80 ml of this preparation must contain 5 g of salicylic acid. The amount of salicylic acid required for the formula is 5×200\/80 = 12.5 g.<\/p>\n

In this case, 12.5 g of salicylic acid is weighed, dissolved in a quantity of ethanol (900<\/sup>), and made up to 200 ml with ethanol (900<\/sup>).<\/p>\n

c) Preparation of 120 g of sodium chloride aqueous solution at a concentration of 1\/60 (w\/w):<\/p>\n

The formula requires the preparation of 120 g of a preparation containing 1 g of sodium chloride and 59 g of water in 60 g of solution.<\/p>\n

Sodium chloride: 1×120\/60 = 2 g<\/p>\n

Water: 59×120\/60 = 118 g.<\/p>\n

d) Calculation of the amount of active substance in 250 ml of retinoic acid stock solution at a concentration of 0.03% (w\/v):<\/p>\n

250×3\/10000 = 0.075 g is obtained.<\/p>\n

e) How many ml should be taken from a 2% (w\/v) potassium permanganate solution to prepare an 80 ml sample at a concentration of 0.25% (w\/v):<\/p>\n

Recalling that a 0.25% concentration is expressed as 0.0025, the amount of substance present in 80 ml is 80×0.0025 = 0.2 g.<\/p>\n

The equivalent volume of the solution containing 2% potassium permanganate for 0.2 g of substance is calculated as 0.2×100\/2 = 10 ml.<\/p>\n

To state briefly: if 10 ml is taken from the 2% (w\/v) potassium permanganate solution and 70 ml of water is added, 80 ml of 0.25% (w\/v) potassium permanganate solution is obtained.<\/p>\n

DILUTION OF STOCK SOLUTIONS<\/strong><\/p>\n

Keeping solutions that are frequently prescribed in our pharmacies readily available as stock solutions, and diluting them to desired concentrations when needed for use in formulations, is important for ensuring efficiency and rapid workflow.<\/p>\n

General Formula;<\/strong><\/p>\n

Based on the formula M1XV1=M2XV2<\/strong><\/p>\n

M1=Concentration of the solution to be prepared (dilute solution)<\/strong><\/p>\n

V1=Volume of the solution to be prepared.<\/strong><\/p>\n

M2=Concentration of the solution used to prepare the desired solution.<\/strong><\/p>\n

V2=Amount to be taken from the concentrated solution, determined by calculation.<\/strong><\/p>\n

Examples;<\/p>\n

a) Preparation of 20 g of a 3% solution from an 8.5% aluminum subacetate stock solution;<\/p>\n

The amount of active ingredient in 20 grams of a preparation containing 3% active ingredient is 3×20\/100 = 0.6 g.<\/p>\n

For 0.6 grams, the amount to be taken from the officinal preparation of 8.5% aluminum subacetate solution during the preparation of the formula is;<\/p>\n

0.6×100\/8.5 = 7.05 g.<\/p>\n

7.05 g of the 8.5% officinal preparation is weighed into a tared container and made up to 20 grams with water.<\/p>\n

To be continued<\/p>\n

Wishing you a good week\u2026<\/p>\n

Spec. Pharm. Ahmet Nezihi Pekcan
\nPekcan Pharmacy – Konya
\npekcanecz@gmail.com
\nTel: (332) 3520657
\nhttp:\/\/www.majistralformul.com\/<\/a><\/p>\n<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"

  Calculation and dilution of stock solutions, scaling up (increasing) and scaling down (reducing) pharmaceutical formulas Dear Colleagues, when preparing compounded formulas, accurate and complete calculation methods are undoubtedly of […]<\/p>\n","protected":false},"author":1,"featured_media":1983,"comment_status":"open","ping_status":"closed","template":"","meta":{"_acf_changed":false,"footnotes":"","_members_access_role":[],"_members_access_error":""},"doc_category":[159],"doc_tag":[],"class_list":["post-9392","docs","type-docs","status-publish","has-post-thumbnail","hentry","doc_category-general-articles"],"acf":[],"year_month":"2026-09","word_count":596,"total_views":"1","reactions":{"happy":"0","normal":"0","sad":"0"},"author_info":{"name":"m921a","author_nicename":"m921a","author_url":"https:\/\/majistraleczacilari.org.tr\/en\/author\/m921a\/"},"doc_category_info":[{"term_name":"General Articles","term_url":"https:\/\/majistraleczacilari.org.tr\/en\/dokuman-kategori\/general-articles\/"}],"doc_tag_info":[],"knowledge_base_info":[],"knowledge_base_slug":[],"_links":{"self":[{"href":"https:\/\/majistraleczacilari.org.tr\/en\/wp-json\/wp\/v2\/docs\/9392","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/majistraleczacilari.org.tr\/en\/wp-json\/wp\/v2\/docs"}],"about":[{"href":"https:\/\/majistraleczacilari.org.tr\/en\/wp-json\/wp\/v2\/types\/docs"}],"author":[{"embeddable":true,"href":"https:\/\/majistraleczacilari.org.tr\/en\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/majistraleczacilari.org.tr\/en\/wp-json\/wp\/v2\/comments?post=9392"}],"version-history":[{"count":1,"href":"https:\/\/majistraleczacilari.org.tr\/en\/wp-json\/wp\/v2\/docs\/9392\/revisions"}],"predecessor-version":[{"id":9394,"href":"https:\/\/majistraleczacilari.org.tr\/en\/wp-json\/wp\/v2\/docs\/9392\/revisions\/9394"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/majistraleczacilari.org.tr\/en\/wp-json\/wp\/v2\/media\/1983"}],"wp:attachment":[{"href":"https:\/\/majistraleczacilari.org.tr\/en\/wp-json\/wp\/v2\/media?parent=9392"}],"wp:term":[{"taxonomy":"doc_category","embeddable":true,"href":"https:\/\/majistraleczacilari.org.tr\/en\/wp-json\/wp\/v2\/doc_category?post=9392"},{"taxonomy":"doc_tag","embeddable":true,"href":"https:\/\/majistraleczacilari.org.tr\/en\/wp-json\/wp\/v2\/doc_tag?post=9392"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}