Відео

If you continue titration beyond the equivalence point, it is a risk that more moles of HCl than the moles of nitrogen in the sample will be added and a falsely high N result may be obtained. A good practice for maintaining similar endpoint color throughout is to compare the current sample with the blank that was titrated first and also to keep a few of the most recent tubes for comparison when working through the batch.

It functions as a protolyte (acid/base) and forms anions (base) proportional to the amount of ammonia that was distilled to the flask. Those anions are then neutralized in the final titration step and the moles of acid needed corresponds to the moles of nitrogen that was in the sample from the beginning.

No, we only use petroleum ether. Diethyl ether was used 30-40 years ago in the Soxhlet method, but we changed the method e.g. for security reasons.

@@app-animal-science-and-welfare thanks so much.

We have noted your request, but this is not among our basal analyses.

Thsnks, requesting if could make more proximate anlysis of feed videos like determing AFD and NDF and etc.@@app-animal-science-and-welfare

No, it was a forage sample that had been dried and milled through a 1 mm screen.

All nitrogen has been distilled over as ammonia to the flask, so the remaining dark liquid in the tube is discarded.

The equation will give an answer as “% N of sample weight”. If you prefer “N, g/kg sample”, you can omit both the “100” in the numerator and the “1000” in the denominator.

What stuff do you mean?

1-2 gram sample, usually 2 gram.

As methyl orange has a lower pKa, more acid will be needed to get the color change.

You need copper (or an alternative catalyst) and you need potassium sulfate. Some decades ago our lab used two small copper nails and a spoon of potassium sulfate for each sample. Appropriate weights to add may be calculated from the specifications of Kjeltabs. Calculation factor for milk is 6.38.

Yes, bunsen burners are commonly used for digestion when a heating block is not at hand. The temperature in our system is 420 °C. Experienced lab technicians may be able to judge completeness of digestion from the color of the solution.

Thank you very much!

Thank you for watching and commenting!

Hej och tack för din fråga. Vi har i studier sett att grisar kan nyttja näringen från grovfoder väl. Hur väl beror naturligtvis på näringssammansättningen i grovfodret. Beroende på grisens ålder (storlek) är också förmågan att bryta ner fiber lite olika. Till suggor och större växande grisar kan grovfoder/vallfoder ingå i foderstaten mellan 10-40% beroende på grisens näringsbehov och det aktuella grovfodret. Det finns generellt fördelar att blötlägga fodret innan utfodring. Stöpning innebär att den blötlagde foderblandningen bara förvaras några timmar i foderanläggningen innan utfodring. Under den tiden hinner en viss enzymatisk påverkan av foderblandningen ske, till exempel aktiveras det i växter naturligt förekommande enzymet fytas som ökar smältbarheten av fosfor. I och med blötläggningen fermenteras fodret, vilket påverkar foderblandningens syra sammansättning. Tillsätts en mjölksyraproducerande bakteriekultur i den blötlagda blandningen kan de koliforma bakterierna som normalt finns på t.ex. spannmålskärnor avdödas genom att mjölksyrabakterierna ökar, mjölksyra bildas och pH sjunker. Detta kan vara positivt för grisens tarmhälsa. Den kombination du beskriver, har jag inte hört om tidigare, men jag tror säkert att det kan fungera väl för grisarna. Huruvida köttet påverkas och blir mer ”bifflikt” är svårt att säga något om. Att blanda in en andel grovfoder/vallfoder gör ofta att slaktkroppen blir mer mager, alltså har en högre köttprocent. Däremot finns det ganska få studier gjorda om fettsyrasammansättning och smak på köttet. Mvh Magdalena Åkerfeldt, forskare SLU och projektledare i projektet Ökat utnyttjande av vall i foder till grisar.

*why for the alternative you did not use ethanol ?* Boric acid 1% with Bromocreosol green / Methyl red indicator. Indicator: 1g of Bromocresole green and 1g of Methyl red, respectively, are dissolved in 1000ml of 95% Ethanol. Add 2.5L 4% (or 5L 2%) Boric acid to a 10L flask. Add deionized water to approx. 9L. Add 100ml Bromocreosole and 70ml Methyl red. Add 3ml 1M NaOH. Adjust volume to 10L and mix. The solution should now shine in green. The NaOH is added because we want a slight response for the blank sample. (Alternatively, but not recommended because > 5.5% Boric acid is classified as cancerogenic, mutagenic, toxic to reproduction : Weigh 100g of Boric acid into a 10L flask, add 2L warm de-ionized water, and mix until it has dissolved. Add water to 9L and proceed as above).

Thank you for those kind words!

You need a blank sample where you use all chemicals but no sample.

Boric acid 1% with Bromocreosol green / Methyl red indicator. Indicator: 1g of Bromocresole green and 1g of Methyl red, respectively, are dissolved in 1000ml of 95% Ethanol. Add 2.5L 4% (or 5L 2%) Boric acid to a 10L flask. Add deionized water to approx. 9L. Add 100ml Bromocreosole and 70ml Methyl red. Add 3ml 1M NaOH. Adjust volume to 10L and mix. The solution should now shine in green. The NaOH is added because we want a slight response for the blank sample. (Alternatively, but not recommended because > 5.5% Boric acid is classified as cancerogenic, mutagenic, toxic to reproduction : Weigh 100g Boric acid into a 10L flask, add 2L warm de-ionized water, and mix until it has dissolved. Add water to 9L and proceed as above).

@@app-animal-science-and-welfare thank you so much , what if you dont add NaOH ? The solution appears in what color? Is it purple? Does % concentration of solution effect the color of indicator for example 1% boric vs 1.5% boric

Analyzed as Kjeldahl-N x 6,25. We use copper sulphate as catalyst. Reference: Nordic committee on food analysis, 1976. Nitrogen. Determination in food and feed according to Kjeldahl, No 6, third edition.

@@app-animal-science-and-welfare Thankyou ❤️❤️❤️

The blank tube contains only the reagents (sulphuric acid and Kjeltabs) and goes through the whole procedure. This is because there is a small contribution to the final result from those reagents and the blank sample is used to correct for that by subtracting the blank value. It is common in many different analyses to have blank samples for that reason.

@@app-animal-science-and-welfare thank you so much 👍

Thank you for your appreciation!